A grocer's daily profit from the sale of two brands of cat food is P(x, y) = (x - 70)(50 - 8x + 4y) + (y - 20)(49 + 5x - 4y) cents, where x is the price per can of the first brand and y is the price per can of the second, each in cents. Currently the first brand sells for 83 cents per can and the second for 39 cents per can. Use marginal analysis to estimate the change in the daily profit that will result if the grocer raises the price of the first brand by one cent, but keeps the price of the second brand unchanged. Answer: _____ cents What is the actual change in profit when the price is changed as in part (a)? Answer: _____ cents