## Step 1: Define the symbolic representation of the problem
The problem involves maximizing an objective function subject to several constraints. The variables are 'milkshakes', 'oranges', 'slices of pizza', and 'chicken drumsticks', which we can denote as $x_0$, $x_1$, $x_2$, and $x_3$ respectively.

## Step 2: Translate the objective function into symbolic notation
The objective function to maximize is $6.35x_0 + 7.44x_1 + 2.49x_2 + 7.43x_3$.

## 3: List the constraints in symbolic notation
The constraints given are:
- $4x_0 + x_1 + 5x_2 + 5x_3 \leq 90$ (protein)
- $3x_0 + 5x_1 + 3x_2 + 4x_3 \leq 79$ (calcium)
- $2x_0 + x_1 + 2x_2 + 5x_3 \leq 70$ (iron)
- $4x_0 + 5x_2 \geq 8$ (protein from milkshakes and slices of pizza)
- $x_1 + 5x_2 \geq 10$ (protein from oranges and slices of pizza)
- $5x_2 + 5x_3 \geq 20$ (protein from slices of pizza and chicken drumsticks)
- $4x_0 + 5x_2 + 5x_3 \geq 14$ (protein from milkshakes, slices of pizza, and chicken drumsticks)
- $x_1 + 5x_3 \geq 15$ (iron from oranges and chicken drumsticks)
- $2x_0 + 2x_2 \geq 6$ (iron from milkshakes and slices of pizza)
- $2x_2 + 5x_3 \geq 5$ (iron from slices of pizza and chicken drumsticks)
- $x_1 + 2x_2 \geq 8$ (iron from oranges and slices of pizza)
- $2x_0 + x_1 \geq 12$ (iron from milkshakes and oranges)
- $x_1 + 5x_3 \leq 52$ (protein from oranges and chicken drumsticks)
- $x_1 + 5x_2 \leq 73$ (protein from oranges and slices of pizza)
- $4x_0 + 5x_2 \leq 78$ (protein from milkshakes and slices of pizza)
- $4x_0 + 5x_2 + 5x_3 \leq 54$ (protein from milkshakes, slices of pizza, and chicken drumsticks)
- $4x_0 + x_1 + 5x_2 + 5x_3 \leq 54$ (total protein)
- $3x_2 + 4x_3 \leq 79$ (calcium from slices of pizza and chicken drumsticks)
- $5x_1 + 3x_2 \leq 61$ (calcium from oranges and slices of pizza)
- $3x_0 + 4x_3 \leq 78$ (calcium from milkshakes and chicken drumsticks)
- $3x_0 + 3x_2 \leq 38$ (calcium from milkshakes and slices of pizza)
- $3x_0 + 5x_1 \leq 61$ (calcium from milkshakes and oranges)
- $3x_0 + 5x_1 + 3x_2 + 4x_3 \leq 61$ (total calcium)
- $2x_0 + 2x_2 \leq 27$ (iron from milkshakes and slices of pizza)
- $2x_0 + x_1 \leq 66$ (iron from milkshakes and oranges)
- $2x_2 + 5x_3 \leq 37$ (iron from slices of pizza and chicken drumsticks)
- $x_1 + 2x_2 \leq 59$ (iron from oranges and slices of pizza)
- $x_1 + 5x_3 \leq 62$ (iron from oranges and chicken drumsticks)
- $2x_0 + x_1 + 5x_3 \leq 49$ (iron from milkshakes, oranges, and chicken drumsticks)
- $2x_0 + 2x_2 + 5x_3 \leq 40$ (iron from milkshakes, slices of pizza, and chicken drumsticks)
- $2x_0 + x_1 + 2x_2 + 5x_3 \leq 40$ (total iron)

## 4: Provide the symbolic representation in JSON format
```json
{
    'sym_variables': [
        ('x0', 'milkshakes'), 
        ('x1', 'oranges'), 
        ('x2', 'slices of pizza'), 
        ('x3', 'chicken drumsticks')
    ], 
    'objective_function': '6.35*x0 + 7.44*x1 + 2.49*x2 + 7.43*x3', 
    'constraints': [
        '4*x0 + x1 + 5*x2 + 5*x3 <= 90',
        '3*x0 + 5*x1 + 3*x2 + 4*x3 <= 79',
        '2*x0 + x1 + 2*x2 + 5*x3 <= 70',
        '4*x0 + 5*x2 >= 8',
        'x1 + 5*x2 >= 10',
        '5*x2 + 5*x3 >= 20',
        '4*x0 + 5*x2 + 5*x3 >= 14',
        'x1 + 5*x3 >= 15',
        '2*x0 + 2*x2 >= 6',
        '2*x2 + 5*x3 >= 5',
        'x1 + 2*x2 >= 8',
        '2*x0 + x1 >= 12',
        'x1 + 5*x3 <= 52',
        'x1 + 5*x2 <= 73',
        '4*x0 + 5*x2 <= 78',
        '4*x0 + 5*x2 + 5*x3 <= 54',
        '4*x0 + x1 + 5*x2 + 5*x3 <= 54',
        '3*x2 + 4*x3 <= 79',
        '5*x1 + 3*x2 <= 61',
        '3*x0 + 4*x3 <= 78',
        '3*x0 + 3*x2 <= 38',
        '3*x0 + 5*x1 <= 61',
        '3*x0 + 5*x1 + 3*x2 + 4*x3 <= 61',
        '2*x0 + 2*x2 <= 27',
        '2*x0 + x1 <= 66',
        '2*x2 + 5*x3 <= 37',
        'x1 + 2*x2 <= 59',
        'x1 + 5*x3 <= 62',
        '2*x0 + x1 + 5*x3 <= 49',
        '2*x0 + 2*x2 + 5*x3 <= 40',
        '2*x0 + x1 + 2*x2 + 5*x3 <= 40'
    ]
}
```

## 5: Implement the optimization problem using Gurobi
```python
import gurobi

def optimize_problem():
    # Create a new Gurobi model
    model = gurobi.Model()

    # Define the variables
    milkshakes = model.addVar(lb=-gurobi.GRB.INFINITY, ub=gurobi.GRB.INFINITY, name="milkshakes")
    oranges = model.addVar(lb=-gurobi.GRB.INFINITY, ub=gurobi.GRB.INFINITY, name="oranges")
    slices_of_pizza = model.addVar(lb=-gurobi.GRB.INFINITY, ub=gurobi.GRB.INFINITY, name="slices of pizza")
    chicken_drumsticks = model.addVar(lb=-gurobi.GRB.INFINITY, ub=gurobi.GRB.INFINITY, name="chicken drumsticks")

    # Define the objective function
    model.setObjective(6.35*milkshakes + 7.44*oranges + 2.49*slices_of_pizza + 7.43*chicken_drumsticks, gurobi.GRB.MAXIMIZE)

    # Add constraints
    model.addConstr(4*milkshakes + oranges + 5*slices_of_pizza + 5*chicken_drumsticks <= 90)
    model.addConstr(3*milkshakes + 5*oranges + 3*slices_of_pizza + 4*chicken_drumsticks <= 79)
    model.addConstr(2*milkshakes + oranges + 2*slices_of_pizza + 5*chicken_drumsticks <= 70)
    model.addConstr(4*milkshakes + 5*slices_of_pizza >= 8)
    model.addConstr(oranges + 5*slices_of_pizza >= 10)
    model.addConstr(5*slices_of_pizza + 5*chicken_drumsticks >= 20)
    model.addConstr(4*milkshakes + 5*slices_of_pizza + 5*chicken_drumsticks >= 14)
    model.addConstr(oranges + 5*chicken_drumsticks >= 15)
    model.addConstr(2*milkshakes + 2*slices_of_pizza >= 6)
    model.addConstr(2*slices_of_pizza + 5*chicken_drumsticks >= 5)
    model.addConstr(oranges + 2*slices_of_pizza >= 8)
    model.addConstr(2*milkshakes + oranges >= 12)
    model.addConstr(oranges + 5*chicken_drumsticks <= 52)
    model.addConstr(oranges + 5*slices_of_pizza <= 73)
    model.addConstr(4*milkshakes + 5*slices_of_pizza <= 78)
    model.addConstr(4*milkshakes + 5*slices_of_pizza + 5*chicken_drumsticks <= 54)
    model.addConstr(4*milkshakes + oranges + 5*slices_of_pizza + 5*chicken_drumsticks <= 54)
    model.addConstr(3*slices_of_pizza + 4*chicken_drumsticks <= 79)
    model.addConstr(5*oranges + 3*slices_of_pizza <= 61)
    model.addConstr(3*milkshakes + 4*chicken_drumsticks <= 78)
    model.addConstr(3*milkshakes + 3*slices_of_pizza <= 38)
    model.addConstr(3*milkshakes + 5*oranges <= 61)
    model.addConstr(3*milkshakes + 5*oranges + 3*slices_of_pizza + 4*chicken_drumsticks <= 61)
    model.addConstr(2*milkshakes + 2*slices_of_pizza <= 27)
    model.addConstr(2*milkshakes + oranges <= 66)
    model.addConstr(2*slices_of_pizza + 5*chicken_drumsticks <= 37)
    model.addConstr(oranges + 2*slices_of_pizza <= 59)
    model.addConstr(oranges + 5*chicken_drumsticks <= 62)
    model.addConstr(2*milkshakes + oranges + 5*chicken_drumsticks <= 49)
    model.addConstr(2*milkshakes + 2*slices_of_pizza + 5*chicken_drumsticks <= 40)
    model.addConstr(2*milkshakes + oranges + 2*slices_of_pizza + 5*chicken_drumsticks <= 40)

    # Solve the model
    model.optimize()

    # Print the solution
    if model.status == gurobi.GRB.OPTIMAL:
        print("Objective: ", model.objVal)
        print("Milkshakes: ", milkshakes.varValue)
        print("Oranges: ", oranges.varValue)
        print("Slices of Pizza: ", slices_of_pizza.varValue)
        print("Chicken Drumsticks: ", chicken_drumsticks.varValue)
    else:
        print("The model is infeasible")

optimize_problem()
```