12. (Vertical Separation) Suppose there is a monopolist manufacturer in the wholesale market with a marginal costat 50, MCM-50, and no fixed cost. There is also a monopolist retailer in the retail market with the retail demand equation: p-170-9. The manufacturer first chooses the wholesale price w, and after observing w the retailer chooses the retail price p. And they work separately from each other. Find the retailer's profit at the equilibrium. A 3,600 B. 1,800 C. None of the other choices are correct. D. 900. T E 0