4. Consider a market with two horizontally differentiated firms, X and Y. Each firm has a marginal cost of 20. They each face demand functions given by the following: QX = 100 – 2PX + PY QY = 100 – 2PY + PX. Calculate the Nash equilibrium prices. (Note: this is covered in the text and in Lecture 9).

"jake’s roof repair has provided the following data concerning its costs: fixed cost per month cost per repair-hour wages and salaries $ 20,900 $ 15.00 parts and supplies $ 7.70 equipment depreciation $ 2,800 $ 0.35 truck operating expenses $ 5,720 $ 1.60 rent $ 4,690 administrative expenses $ 3,850 $ 0.50 for example, wages and salaries should be $20,900 plus $15.00 per repair-hour. the company expected to work 2,600 repair-hours in may, but actually worked 2,500 repair-hours. the company expects its sales to be $47.00 per repair-hour. required: compute the company’s activity variances for may."