Suppose college graduates earn $25 an hour and high school graduates earn $15 an hour. Suppose too that the marginal product of college graduates at Johnson tools is five hammers per hour, while the marginal product of high school graduates is four hammers per hour (regardless of the number of each type of worker employed). What if the marginal product of high school graduates was instead two hammers per hour? What is the critical difference in productivity (in percentage terms) at which the type of worker hired changes