A professor's graduate assistant can grade a quiz in 40 seconds. Over the course of an academic year he assists with 6 sections of a course with an average of 30 students with 10 quizzes in each section

If he is paid $8 an hour, how much is his annual quiz-grading labor cost to the university?
A) $60
B) $160
C) $576
D) $576,000

B