Two mechanics were working on your car. One can complete the given job in six hours, but the new guy takes 7 hours. They worked together for the first two hours, but then the first guy left to help another mechanic on a different job. How long will it take the new guy to finish your car?	Answers:
A) 7 / 4
B) 4 / 3
C) 15 / 4
D) 10 / 3
E) 64 / 21

Rationale: rate ( 1 ) = 1 / 6 rate ( 2 ) = 1 / 7 combined = 13 / 42 work done in 2 days = 13 / 21 work left = 8 / 21 rate * time = work left 1 / 8 * time = 8 / 21 time = 64 / 21 e
Answer: E