21. Please solve

A company has found that the marginal cost (in thousands of dollars) to produce x central air conditioning units is C (x) = = ", where x is the number of units produced (a) Find the cost function, given that the company incurs a fixed cost of $14,000 even if no units are built. (b) The company will seek a new source of investment income if the cost is more than $22,000 to produce 5 units. Should they seek this new source? (a) What substitution should be used to determine the cost function? Use the quantity as the substitution, u = , so that du = ( )dx The cost function is C(x) = (b) Therefore, the cost of producing 5 units is $ so the company seek a new source of investment income. (Round to the nearest dollar as needed.)