What are implicit costs? an implicit cost is a. a cost that remains constant as output changes. b. a cost that changes as output changes. c. a cost incurred in the long run. d. a nonmonetary opportunity cost. e. the highest-valued alternative that must be given up to engage in an activity. how are implicit costs different from explicit costs? a. an explicit cost is a cost that involves spending money, while an implicit cost is a nonmonetary cost. b. an explicit cost is not an opportunity cost, while an implicit cost is an opportunity cost. c. an explicit cost is a cost incurred holding output constant, while an implicit cost is a cost incurred as output changes. d. an explicit cost is a cost incurred in the short run, while an implicit cost is a cost incurred in the long run. e. both a and b?