Here's the formulation of the Linear Program (LP) and the Gurobi code to solve it:

**Decision Variables:**

* `x1`: Investment in the video game company.
* `x2`: Investment in the camera company.
* `x3`: Investment in the cell phone company.
* `x4`: Investment in the laptop company.

**Objective Function:**

Maximize the total return on investment:

```
Maximize 0.07*x1 + 0.03*x2 + 0.09*x3 + 0.07*x4
```

**Constraints:**

* **Total Investment:** The total investment cannot exceed $300,000.

```
x1 + x2 + x3 + x4 <= 300000
```

* **Laptop Investment:** The investment in the laptop company cannot exceed the investment in the video game company.

```
x4 <= x1
```

* **Camera Investment:** The investment in the camera company cannot exceed the investment in the cell phone company.

```
x2 <= x3
```

* **Laptop Investment Limit:**  At most 15% of the total investment can be in the laptop company.

```
x4 <= 0.15 * 300000 
```

* **Non-negativity:** All investments must be non-negative.

```
x1, x2, x3, x4 >= 0
```

```python
import gurobipy as gp
from gurobipy import GRB

# Create a new model
m = gp.Model("investment_optimization")

# Create decision variables
x1 = m.addVar(lb=0, name="video_game")
x2 = m.addVar(lb=0, name="camera")
x3 = m.addVar(lb=0, name="cell_phone")
x4 = m.addVar(lb=0, name="laptop")

# Set objective function
m.setObjective(0.07*x1 + 0.03*x2 + 0.09*x3 + 0.07*x4, GRB.MAXIMIZE)

# Add constraints
m.addConstr(x1 + x2 + x3 + x4 <= 300000, "total_investment")
m.addConstr(x4 <= x1, "laptop_vs_video_game")
m.addConstr(x2 <= x3, "camera_vs_cell_phone")
m.addConstr(x4 <= 0.15 * 300000, "laptop_limit")

# Optimize model
m.optimize()

# Print results
if m.status == GRB.OPTIMAL:
    print(f"Optimal return: ${m.objVal:.2f}")
    print(f"Video Game Investment: ${x1.x:.2f}")
    print(f"Camera Investment: ${x2.x:.2f}")
    print(f"Cell Phone Investment: ${x3.x:.2f}")
    print(f"Laptop Investment: ${x4.x:.2f}")
elif m.status == GRB.INFEASIBLE:
    print("The model is infeasible.")
else:
    print(f"Optimization terminated with status {m.status}")

```
