4. Suppose that the demand equation for a monspolist's product is p =400-2x and the 400 average cost function is c(x) =0.2x + 4+ , where x is the number of units, and both X p and c(x) are expressed in dollars per unit. a. Determine the level of output ( i.e. find the value of x ) at which profit is maximized. b. Determine the price at which maximum profit occurs. c. Determine the maximum profit