Answer: The cost increases $2.50 for every additional pair of shoes rented.
Explanation:
Given: Number of Pairs of Shoes (x): 1 2 3 4 5
Cost C(x) : $2.50 $5.00 $7.50 $10.00 $12.50
Let C(x) be the cost function for the given situation
Thus the rate of change of the function from x=1 to x=5=

Similarly , we can check for every interval the rate of change in price= $2.50
Thus, we can say "The cost increases $2.50 for every additional pair of shoes rented."