Which of the following is NOT true at an individual's optimal level of schooling?

a.

The marginal benefit associated with an additional year of schooling is equal to the marginal cost.

b.

The internal rate of return on schooling is equal to the market interest rate.

c.

The present value of lifetime labour earnings is maximized.

d.

Earnings are still increasing as years of schooling increase.

e.

None of the above.