Please help me with these microeconomics questions:

13. The difference between economic and accounting costs is the inclusion of . . .

(a) private costs.

(b) external costs.

(c) labor costs.

(d) opportunity costs.

(e) depreciation costs.

14. The short run marginal cost curve in the traditional microeconomic model eventually rises because of . . .

(a) diminishing marginal returns.

(b) rising fixed costs.

(c) diseconomies of scale.

(d) diminishing marginal revenues.

(e) increasing marginal productivity of variable inputs.

15. Economies of scale refer to a firm's . . .

(a) marginal costs increasing as output increases.

(b) long-run average costs decreasing as output increases.

(c) total costs decreasing as output increases.

(d) opportunity costs decreasing as output increases.

(e) transactions costs decreasing as output increases.

16. The economists' view of market power and competition is that . . .

(a) competition and market power are both desirable.

(b) competition is generally desirable but market power is normally undesirable.

(c) competition is generally undesirable but market power is normally desirable.

(d) competition and market power can both be undesirable.

(e) None of the above.

17. In a perfectly competitive market, the demand curve facing each individual seller is assumed to be . . .

(a) perfectly inelastic.

(b) moderately inelastic.

(c) unit elasticity.

(d) moderately elastic.

(e) perfectly elastic.