The market demand for brand X has been estimated as Qx = 1,500 - 3Px - 0.05I - 2.5Py + 7.5Pz where Px is the price of brand X, I is per-capita income, Py is the price of brand Y, and Pz is the price of brand Z. Assume that Px = $2, I = $20,000,Py = $4, and Pz = $4. a. With respect to changes in per-capita income, what kind of good is brand X? b. How are brands X and Y related? c. How are brands X and Z related? d. How are brands Z and Y related? e. What is the market demand for brand X?