21) The main difference between the short run and the long run
A) in the short run all inputs are fixed, while in the long
run all inputs are variable.
B) in the short run the firm varies all of its inputs to find
the least-cost combination of inputs.
C) in the short run, at least one of the firm's input levels
D) in the long run, the firm is making a constrained decision
about how to use existing plant and equipment efficiently.
22) The "law of diminishing marginal returns" applies
A) the short run, but not the long run.
B) the long run, but not the short run.
C) both the short run and the long run.
D) neither the short run nor the long run.
23) An implicit cost is defined as:
A) the opportunity cost of using a resource that is not
explicitly paid out by the firm.
B) the difference between an input's explicit cost and its
C) the amount by which economic profit exceeds accounting
D) the amount by which the money spent on an input to
production exceeds its opportunity cost.