Suppose that in Tasmania the income elasticity of high-fat minced lamb meat is -0.20 and the price elasticity of high-fat minced lamb meat is -0.80.Suppose also that in Tasmania the cross-price elasticity of high-fat minced lamb and low-fat minced beef is +0.3 and the cross-price elasticity of high-fat minced lamb and onions is -0.2.

a.If the demand for high-fat minced lamb is linear (a straight line), is the marginal revenue for positive or negative.Explain why.