There are three groups in a community. Their demand curves for public television in hours of programming,

Question:

There are three groups in a community. Their demand curves for public television in hours of programming, T, are given respectively by
W1 = $200 - T,
W2 = $240 - 2T,
W3 = $320 - 2T.
Suppose public television is a pure public good that can be produced at a constant marginal cost of $200 per hour.
a. What is the efficient number of hours of public television?
b.How much public television would a competitive private market provide?