Which of the four costs relevant to aggregate production planning is the most difficult to accurately measure?

One of the scarce resources that constrain our behavior is time. each of us has only 24 hours in a day, and we must allocate our time in a given day among competing alternatives. how do you go about allocating your time in a given day among competing alternatives? how do you go about weighing the alternatives? once you choose a most important use of time, why do you not spend all your time on that activity? a. as more and more time is spent on one activity, the opportunity cost of that activity in terms of other activities rises. b. as less and less time is spent on one activity, the opportunity cost of that activity in terms of other activities rises. c. as more and more time is spent on one activity, the opportunity cost of that activity in terms of other activities falls. d. b and c only.