Education Has an External Benefit

Education has an external benefit.So to achieve the efficient level of education,an education voucher must equal the difference between the

A) marginal (private) cost and the marginal social benefit.
B) marginal (private) benefit and the marginal social benefit.
C) marginal social benefit and the marginal (private) cost.
D) dollar price and marginal (private) cost.
E) marginal (private) cost and the marginal social cost.