When Bob plays the piano for four hours, and his grade on the English test is 90 percent. Last week, after playing for four hours, Bob considered playing the piano for a fifth hour. He decided to play for one additional hour and cut his study time by one hour, but his English grade fell to 70 percent. What can you conclude about Bob's marginal benefit and marginal cost of the fourth hour of playing the piano? Question content area bottom Part 1 A. The marginal cost of the fourth hour of playing the piano exceeded its marginal benefit. B. The marginal benefit from the fourth hour of playing the piano exceeded its marginal cost. C. The drop of 20 percentage points on an English test exceeded the marginal benefit from a fifth hour of playing the piano. D. The marginal benefit from the fourth hour of playing the piano exceeded the marginal cost of dropping 20 percentage points on an English test