Working at a constant rate, P can finish a job in 3 hours. Q, also working at a constant rate, can finish the same job in 15 hours. If they work together for 2 hours, how many more minutes will it take P to finish the job, working alone at his constant rate?	Choose the correct choice from the following answers:  A) 30  B) 36  C) 40  D) 45  E) 48

Rationale: each hour they complete 1 / 3 + 1 / 15 = 2 / 5 of the job . in 2 hours , they complete 2 ( 2 / 5 ) = 4 / 5 of the job . the time for p to finish is ( 1 / 5 ) / ( 1 / 3 ) = ( 3 / 5 ) hour = 36 minutes the answer is b .
Answer: B