4. (25 points) Let the market demand for rye bread be given by Q = 50 250Pre + 400P wheat, where Q is monthly demand in number of loaves, monthly income in dollars, Pry is the price of a loaf of rye bread, and price of a loaf of wheat bread. If I = $1,000, Pre = $2, and Pwheat = $3, the following (based on 10% changes in denominators): (a) the arc price elasticity of demand for rye bread (b) the arc price elasticity of demand for wheat bread (c) the arc cross-price elasticity of demand for rye bread