Interpreting Function Notation, Graphs, and Context

You are a restaurant trying to determine the price of your salads. Let

• $P_s=\text{Price total of salad}$,
• $A_l=\text{Amount of lettuce ordered}$,
• $A_c=\text{Amount of cheese ordered}$,
• $A_t=\text{Amount of tomatoes ordered}$, and
• $A_d=\text{Amount of dressing ordered}$.

Assume the only ingredients on your salad are lettuce, cheese, tomatoes, and dressing. Which of the equations below represents the most likely kind of relationship between the five variables defined above?