Problem Set question: The cost, in dollars, of producing _ units of a certain item is given by C(z) = 0.0423 - 20r + 200 (a) Find the marginal cost function. MC (@)= (b) Find the marginal cost when 70 units of the item are produced. The marginal cost when 70 units are produced is $ Number (c) Find the actual cost of increasing production from 70 units to 71 units. The actual cost of increasing production from 70 units to 71 units is $ Number