Working at a constant rate, P can finish a job in 4 hours. Q, also working at a constant rate, can finish the same job in 15 hours. If they work together for 3 hours, how many more minutes will it take P to finish the job, working alone at his constant rate?	Choose the correct choice.
A) 5
B) 8
C) 10
D) 12
E) 15
Each hour they complete 1/4 + 1/15 = 19/60 of the job.   In 3 hours, they complete 3(19/60) = 19/20 of the job.   The time for P to finish is (1/20) / (1/4) = (1/5) hour = 12 minutes   The answer is 12.
<result>D</result>
Working at a constant rate, P can finish a job in 4 hours. Q, also working at a constant rate, can finish the same job in 15 hours. If they work together for 3 hours, how many more minutes will it take P to finish the job, working alone at his constant rate?