If the government decides to provide public colleges, what tuition will these colleges charge to achieve the

Question:

If the government decides to provide public colleges, what tuition will these colleges charge to achieve the efficient number of students? How much will taxpayers have to pay?
The marginal cost of educating a student is a constant $4,000 a year and Figure 16.5 shows the students€™ marginal benefit curve. Suppose that college education creates an external benefit of a constant $2,000 per student per year.