With shells, the volume is given by
Admission to the zoo costs $15 per person.
The graph y = 15x correctly represents the total cost for a group to visit the zoo.
Given;
Admission to the zoo costs per person = $15
Let:
The total number of people visiting the zoo = x
The total cost for a group to visit the zoo = y
So, y ∝ x
y = 15x
Therefore, the graph y = 15x correctly represents the total cost for a group to visit the zoo.
You said that P = I · R · T
Divide each side by I · R : P / (I·R) = T