Cost, revenue, and profit are in dollars and x is the number of units. A firm knows that its marginal cost for a product is MC = 3x + 25, that its marginal revenue is MR = 57 - 5x, and that the cost of production of 80 units is $11,760. (a) Find the optimal level of production. units (b) Find the profit function. P(x) = (c) Find the profit or loss at the optimal level. There is a loss of $