Demand for some good X is QX = 450 – 20PX + 3Y - 10PZ where Y is income, PX is price of a X, and PZ is the price of a related good. Assume that PX and PZ are both $10 and income is $200.
Calculate the cross-price elasticity of demand of X (with respect to a change in the price of Z). If the price of Z increases by 10 percent, what is the percentage change in quantity demanded of X?