6. dl. Ao o2 0 40 20 30 40 S0 60 70 Toothbrushes Refer to the figure. Suppose the economy is at point A. What is the opportunity cost of increasing the production of toothbrushes by 10 units? 5 toasters b. 10 toasters . 15 toasters d. 20 toasters . Why are production possibilities frontiers usually bowed outward? . constant opportunity cost b. increasing opportunity st . decreasing opportunity cost d. increasing productivity . What does making decisions \"at the margin\" mean? . that people make those decisions that do not impose a marginal cost . that people evaluate how easily a decision can be reversed if problems arise . that people compare the marginal costs and marginal benefits of each decision . that people always calculate the marginal dollar costs for each decision