Answer:
They buy at wholesale and sell at an 80% markup. The retail prices are;
0 - 20 pairs.
= 25 * 1.80
= $45.00
21 - 40 pairs
= 23 * 1.80
= $41.40
41 - 60 pairs
= 21 * 1.80
= $37.80
61 - 80 pairs
= 19 * 1.80
= $34.20
81 or more pairs
= 17 * 1.80
= $30.60