P, Q, and R working separately can do a piece of work in 50, 100, and 300 days respectively. If they work on alternate days, P works on thefi rst day, Q works on the second day, R works on the third day and then again P works on the fourth day and so on, then in how many days, the work will be completed?

A

60 days

B

50 days

C

40 days

D

90 days