1. Assume that for Indy, one hour of study time in economics is perfectly substitutable for an hour of study time in calculus. Indy has exams in both subjects tomorrow and he determines that if he spends all of his time studying economics, he will receive scores of 96 on his economics exam and 45 on his calculus exam. If he studies only calculus, his economics score will be 81 and his calculus score will be 90. Based on this information and assuming that Indy has no better alternative use of his time, what is the opportunity cost of improving his economics score by one (1) point?