```json
{
  "sym_variables": [
    ("x0", "milligrams of calcium"),
    ("x1", "milligrams of vitamin A"),
    ("x2", "milligrams of magnesium"),
    ("x3", "milligrams of zinc")
  ],
  "objective_function": "7*x0 + 1*x1 + 1*x2 + 4*x3",
  "constraints": [
    "9*x1 + 1*x3 >= 53",
    "9*x0 + 1*x3 >= 70",
    "9*x0 + 6*x2 + 1*x3 >= 70",
    "9*x0 + 9*x1 + 6*x2 >= 70",
    "9*x0 + 6*x2 + 1*x3 >= 84",
    "9*x0 + 9*x1 + 6*x2 >= 84",
    "9*x0 + 9*x1 <= 110",
    "6*x2 + 1*x3 <= 236",
    "9*x1 + 1*x3 <= 223",
    "9*x0 + 9*x1 + 6*x2 + 1*x3 <= 223",
    "9*x0 + 9*x1 + 6*x2 + 1*x3 <= 342" 
  ]
}
```

```python
import gurobipy as gp

try:
    # Create a new model
    m = gp.Model("kidney_support")

    # Create variables
    calcium = m.addVar(vtype=gp.GRB.CONTINUOUS, name="calcium")
    vitamin_a = m.addVar(vtype=gp.GRB.CONTINUOUS, name="vitamin_a")
    magnesium = m.addVar(vtype=gp.GRB.CONTINUOUS, name="magnesium")
    zinc = m.addVar(vtype=gp.GRB.CONTINUOUS, name="zinc")


    # Set objective function
    m.setObjective(7*calcium + 1*vitamin_a + 1*magnesium + 4*zinc, gp.GRB.MAXIMIZE)

    # Add constraints
    m.addConstr(9*vitamin_a + 1*zinc >= 53, "c1")
    m.addConstr(9*calcium + 1*zinc >= 70, "c2")
    m.addConstr(9*calcium + 6*magnesium + 1*zinc >= 70, "c3")
    m.addConstr(9*calcium + 9*vitamin_a + 6*magnesium >= 70, "c4")
    m.addConstr(9*calcium + 6*magnesium + 1*zinc >= 84, "c5")
    m.addConstr(9*calcium + 9*vitamin_a + 6*magnesium >= 84, "c6")
    m.addConstr(9*calcium + 9*vitamin_a <= 110, "c7")
    m.addConstr(6*magnesium + 1*zinc <= 236, "c8")
    m.addConstr(9*vitamin_a + 1*zinc <= 223, "c9")
    m.addConstr(9*calcium + 9*vitamin_a + 6*magnesium + 1*zinc <= 223, "c10")
    m.addConstr(9*calcium + 9*vitamin_a + 6*magnesium + 1*zinc <= 342, "c11") # Resource constraint


    # Optimize model
    m.optimize()

    if m.status == gp.GRB.OPTIMAL:
        print('Obj: %g' % m.objVal)
        for v in m.getVars():
            print('%s %g' % (v.varName, v.x))
    elif m.status == gp.GRB.INFEASIBLE:
        print('Optimization was infeasible.')


except gp.GurobiError as e:
    print('Error code ' + str(e.errno) + ': ' + str(e))

except AttributeError:
    print('Encountered an attribute error')
```
