The social cost of a transaction is .
O the sum of fixed costs and opportunity costs.
O the sum of fixed and variable costs.
O the sum of private and external costs.
O the difference between the private and external costs.
O the difference between the total cost and opportunity cost.

Robert black, regional manager for ford in texas and oklahoma, faced a dilemma. the ford f-150 pickup truck was the best-selling pickup ever, yet ford's headquarters in detroit had decided to introduce a completely redesigned f-150. how could mr. black sell both trucks at the same time? he still had "old" f-150s in stock. in his advertising, mr. black referred to the new f-150s as follows: "not a better f-150. just the only truck good enough to be the next f-150." this statement represents ford's of the new f-150.