1. If representative firm with total cost given by TC = 20 + 20q + 5q2 operates in competitive industry where the short-run market demand and supply curves are given by QD = 1,400 - 40P and QS = -400 + 20P, the number of firms operating in short run will be:

2. If the profit-maximizing markup price is marginal cost times 2, the elasticity of demand must be:

3. A representative firm with short-run total cost given by TC = 50 + 2q + 2q2 operates in a competitive industry where the short-run market demand and supply curves are given by QD = 1,690 - 40P and QS = -390 + 20P. Its short-run profit-maximizing level of output is:

4. The XYZ Steel Company produces its own coal for use in its production facility. The demand for steel is given by Ps = 500 - 2Qs and the total cost of producing steel is given by TCs = 100Qs, where Qs is tons of steel per week. The price of coal in a perfectly competitive market outside the firm is $250 per ton, and the total cost of producing coal is given by TCc = 40 + 5Qc2, where Qc is tons of coal per week. How much steel should the XYZ Company produce?