12. [S] [C] A farmer is using two compounds - a nitrogen-rich compound and a phosphorus-rich compound - to improve crop yields. If the farmer uses N tons of the nitrogen compound and P tons of the phosphorus compound, then the crop's yield can be modeled by Y(N, P) = BN2Pe_N_2P, where ,8 is a constant which depends on the crop. (a) What happens to the crop yield if the farmer uses none of either of the compounds? (b) What happens to the crop yield if the farmer uses too much of either of the compounds? (Express this using limits.) (0) How much of each compound should the farmer use to attain the best yield'.\"r