Rolf's Supermarkets now sell 12,000 lbs. of grapefruit per week at a price of $0.45 per pound. An economist has reported to management that the arc elasticity of demand for the grapefruit over the price range $0.45 to $0.35 per pound is -2.0. If Rolf's lowers its grapefruit price to $0.35 per pound, determine how many grapefruit it will sell per week and what the change in its total revenue (TR) from grapefruit sales will be.