4. 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?

(Please provide a different approach to solve this question, other than the already given one)