Cliff's Candy produces and sells boxes of chocolates. When Cliff produces and sells his profit-maximizing quantity of 1,000 boxes, the average total cost is $3.00. If Cliff were to produce 1,100 boxes, the average total cost would be $2.50. Which of the following inefficiencies of monopolistically competitive markets is described in this scenario? a. Product-variety externality b. Business-stealing externality c. Markup over marginal cost d. Excess capacity