Answer:
(a) Concept of consumer surplus
(b) Concept of producer surplus
(c) Neither
Explanation:
(a) The first statement illustrates consumer surplus because it indicates the price I am willing to pay up for the used textbook ($67) and the price I bought the used textbook ($58). Consumer surplus = $67 - $58 = $9
(b) The second statement illustrates producer surplus because it indicates the price I sold the jersey sweater ($31) and the price I was willing to sell ($24). Producer surplus = $31 - $24 = $7
(c) The third statement neither illustrates consumer not producer surplus because it did not indicate the price I was willing to sell the used laptop.