Suppose mountain spring water can be produced at no cost and that the demand and marginal revenue curves for mountain spring water are given as​ follows: Q = 6000 - 5P MR = 1200 - 0.3QWhat is the​ profit-maximizing price of a​ monopolist? a. ​$800 b. ​$600 c. ​$400 d. ​$900 e. None of the above