Define the function average-price

Define the function average-price. It consumes a list of toy prices and computes the average price of a toy. The average is the total of all prices divided by the number of toys.
Iterative Refinement: First develop a function that works on non-empty lists. Then produce a checked function (see section 7.5) that signals an error when the function is applied to an empty list.

find the cost of your paper