A city has three neighborhoods with three demand curves for public radio in hours of broadcasting, B, are given by the following:

N1 = $ 100 B

N2 = $ 120 2B

N3 = $ 160 2B

Public radio is a public good that can be produced at constant marginal cost of $100 per hour.

a). Calculate the efficient number of hours of public radio broadcasting.

b). How many hours of public radio broadcasting would a competitive market provide?