Asupply curve a. tells us the lowest price at which someone is willing to sell tells us the lowest price at which someone is willing to sell b. tells us the minimum minimum that someone is willing to pay for an additional unit of a good or service c. tells us that marginal cost decreases as the quantity tells us that marginal cost decreases as the quantity purchased increases purchased increases d. shows us that the highest price that someone is willing to pay for an additional unit of a good or service falls as the quantity decreases falls as the quantity decreases