Two tap P and Q can fill a tank in 15 and 25 minutes respectively both taps are opened together

Two tap P and Q can fill a tank in 15 and 25 minutes respectively both taps are opened together. When tank is filled  8/15 a leakage tap is opened. leakage tap’s efficiency is  1/4 of the net efficiency of taps P and Q together. In how much time tank will get filled.

Sol: