Explain why each of the following might serve to deter entry of a competitor.
(a) Maintaining excess production capacity
(b) Promising customers that you will undercut any rival
(c) Selling your output at a price below that at which marginal revenue equals marginal cost (Hint: Assume entrants are unsure about what your marginal costs are. Why would they be deterred from entering if they believed you have low marginal costs? Why might a lower price lead them to think that you had low marginal costs?)
(d) Offering a discount to customers who sign up for long-term contracts