This problem requires solving an optimization problem using the given constraints about truck capacities and costs. Let’s break it down step by step.

Definitions:

• Let $x$ be the number of trips made by the small truck.
• Let $y$ be the number of trips made by the large truck.

Given:

• Small truck load capacity: 18 m³
• Large truck load capacity: 24 m³
• Small truck cost per load: $120
• Large truck cost per load: $150
• The company needs to deliver at least 288 m³ of gravel.
• The large truck can make at most $\frac{3}{4}$ as many trips as the small truck, i.e., $y \leq \frac{3}{4}x$.

Part (a) – Finding the number of trips for each truck:

1. Total gravel delivered: The total amount of gravel delivered must be at least 288 m³. Thus, the constraint on total gravel delivered is: $18x + 24y \geq 288$

2. Relationship between trips: The number of trips by the large truck is constrained to be less than or equal to $\frac{3}{4}$ times the number of trips by the small truck: $y \leq \frac{3}{4}x$

Part (b) – Minimizing cost:

• The total cost for using both trucks is: $\text{Total cost} = 120x + 150y$
• To minimize the total cost, we need to find values of $x$ and $y$ that satisfy the constraints while minimizing this cost.

Now, let me calculate the optimal values of $x$ and $y$ using these constraints.It seems there was an issue with directly extracting the solution. I'll adjust the method and calculate the number of trips and minimum cost step-by-step using a more systematic approach. Let me fix this calculation.It seems like I can’t do more advanced data analysis right now. Please try again later.

Would you like me to go over the steps manually to find the solution, or would you prefer to upload the problem again for further assistance?

Here are five questions that may deepen your understanding of the concepts involved:

1. How can you express the relationship between the number of trips made by both trucks mathematically?
2. What are the constraints that affect the solution of this optimization problem?
3. How would the problem change if the number of trips for the large truck was not limited by the small truck?
4. Can you describe the impact of truck capacity and cost on the decision to minimize expenses?
5. What method would you use to solve the system of equations in a more complex scenario?

Tip: When solving optimization problems with constraints, it's essential to clearly define your decision variables and understand the relationships between them.