## Step 1: Define the symbolic representation of the variables
The variables are 'CBRN platoons', 'mechanized infantry companies', and 'water purification units'. Let's denote them as $x_0$, $x_1$, and $x_2$ respectively.

## Step 2: Convert the natural language objects into symbolic variables
The symbolic variables are $x_0$ for 'CBRN platoons', $x_1$ for 'mechanized infantry companies', and $x_2$ for 'water purification units'.

## 3: Define the objective function in symbolic notation
The objective function to minimize is $8x_0 + 7x_1 + 4x_2$.

## 4: Define the constraints in symbolic notation
The constraints are:
- $11x_1 + 18x_2 \geq 32$
- $7x_0 + 11x_1 \geq 24$
- $7x_0 + 11x_1 + 18x_2 \geq 24$
- $18x_1 + 3x_2 \geq 26$
- $x_0 + 18x_1 \geq 12$
- $x_0 + 18x_1 + 3x_2 \geq 12$
- $7x_0 + 11x_1 + 18x_2 \leq 49$
- $x_0, x_1, x_2$ are integers.

## 5: Provide the symbolic representation of the problem
```json
{
'sym_variables': [('x0', 'CBRN platoons'), ('x1', 'mechanized infantry companies'), ('x2', 'water purification units')],
'objective_function': '8*x0 + 7*x1 + 4*x2',
'constraints': [
    '11*x1 + 18*x2 >= 32',
    '7*x0 + 11*x1 >= 24',
    '7*x0 + 11*x1 + 18*x2 >= 24',
    '18*x1 + 3*x2 >= 26',
    'x0 + 18*x1 >= 12',
    'x0 + 18*x1 + 3*x2 >= 12',
    '7*x0 + 11*x1 + 18*x2 <= 49',
    'x0, x1, x2 are integers'
]
}
```

## Step 6: Write the Gurobi code to solve the optimization problem
```python
import gurobi

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

    # Define the variables
    x0 = model.addVar(name="CBRN_platoons", vtype=gurobi.GRB.INTEGER)
    x1 = model.addVar(name="mechanized_infantry_companies", vtype=gurobi.GRB.INTEGER)
    x2 = model.addVar(name="water_purification_units", vtype=gurobi.GRB.INTEGER)

    # Define the objective function
    model.setObjective(8 * x0 + 7 * x1 + 4 * x2, gurobi.GRB.MINIMIZE)

    # Add constraints
    model.addConstr(11 * x1 + 18 * x2 >= 32)
    model.addConstr(7 * x0 + 11 * x1 >= 24)
    model.addConstr(7 * x0 + 11 * x1 + 18 * x2 >= 24)
    model.addConstr(18 * x1 + 3 * x2 >= 26)
    model.addConstr(x0 + 18 * x1 >= 12)
    model.addConstr(x0 + 18 * x1 + 3 * x2 >= 12)
    model.addConstr(7 * x0 + 11 * x1 + 18 * x2 <= 49)

    # Optimize the model
    model.optimize()

    # Print the solution
    if model.status == gurobi.GRB.OPTIMAL:
        print("Optimal solution found.")
        print(f"CBRN platoons: {x0.varValue}")
        print(f"Mechanized infantry companies: {x1.varValue}")
        print(f"Water purification units: {x2.varValue}")
        print(f"Objective function value: {model.objVal}")
    else:
        print("No optimal solution found.")

solve_optimization_problem()
```