PLEASE ANSWER

A) A local shoe store buys shoes at a wholesale price and then marks them up 80% to calculate the retail price. The wholesale price varies, depending on the quantity of shoes purchased. (2 points)
Quantity 0-20 pairs 21-40 pairs 41-60 pairs 61-80 pairs 81 or more pairs
Wholesale Price
(per pair) $25.00 each $23.00 each $21.00 each $19.00 each $17.00 each

Write an equation that could be used to find the retail price for each range. How do you know the equation will work consistently for each range?