Question: Pesticide an area of land is to be sprayed with two brands of pesticide; x liters of brand 1 and y liters of brand 2. If the number of thousands of insects killed is given by
f(x, y) = 10,000 - 6500e-0.01x - 3500e-0.02y
how many insects would be killed if 80 liters of brand 1 and 120 liters of brand 2 were used?