A monopolist produces widgets at AC = MC =10. There are two types of consumers, type A's demand is given by QA = 60 - P and type B demand is given by QB = 45 - 0.5P.

a) Suppose the monopolist knows there are two types of consumers and can tell who is who. Which price would the monopolist charge to each type of consumer?

b) Suppose the monopolist knows there are two types of consumers, but cannot tell who is who. Which two part tariff would the monopolist charge?

c) Suppose the monopolist does not know there are two types of consumers, but knows just the aggregate demand (QA + QB). What would be the monopoly price?