Suppose the marginal benefit of writing a contract is $80 , independent of its length. Find the optimal contract length when the marginal cost of writing a contract of length L is: Instruction: Enter your responses rounded to two decimal places. a. MC ( L ) = 5 + 2 L . b. MC ( L ) = 20 + 3 L . c. What happens to the optimal contract length when the marginal cost of writing a contract declines? .