A change in the level of an economic activity is desirable and should be undertaken as long as the marginal benefits exceed the ____.

Note: Hand written solution should be avoided.

a) At 200 units of the activity, marginal benefit is $__________ and marginal cost is $__________. b) Adding the 200th unit of the activity causes net benefit to __________ (increase, decrease) by $__________. c) At 700 units of the activity, marginal benefit is $__________ and marginal cost is $__________. d) Subtracting the 700th unit of the activity causes net benefit to __________ (increase, decrease) by $__________. e) The optimal level of the activity is __________units. At the optimal level of the activity, marginal benefit is $__________ and marginal cost is $__________.

Answer the given question with a proper explanation and step-by-step solution.   what is the answer?