Pipes A, B and C can fill an empty tank in $$\frac{{30}}{7}$$ hours, if all the three pipes are opened simultaneously. A and B are filling pipes and C is an emptying pipe. Pipe A can fill tank in 15 hours and pipe C can empty it in 12 hours. In how long (in hours) can pipe B alone fill the empty tank?

A. 4

B. 6

C. 3

D. 5

Answer: Option A

Solution (By Examveda Team)

A + B + C = 14
4 + B - 5 = 14
B = 15 unit
B = $$\frac{{60}}{{15}}$$ = 4 hours