Thirsty Thelma owns and operates a small lemonade stand. When Thelma is producing a low quantity of lemonade she has few workers and her equipment is not being fully utilized. Because she can easily put her idle resources to use,

a. the marginal cost of an extra worker is large.
b. the marginal cost of one more glass of lemonade is smaller than if output were high.
c. her lemonade stand is likely to be crowded with workers.
d. the marginal product of an extra worker is small.