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 + 30, that its marginal revenue is MR = 70 5x, and that the cost of production of 60 units is $7,400. (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 |---Select--- v of $