There are 4 outlet of pipes of same capacity fixed one above the other to a water tank. The 1st pipe is at the bottom level & the 4th pipe is at three-fourth of the height of the tank .The 3rd pipe is equidistant from the 2nd pipe and the 4th pipe. The 2nd pipe is equidistant from the 1st and the 3rd. The capacity of each pipe is such that it can empty a full tank in 4hr. whereas one inlet pipe can fill the empty tank in 1hr. The pipe is opened to fill the empty tank & after 1hr it is closed. Then all the outlet pipes are opened. When the tank is full all the 4 pipes are opened together and shut after 1hr. If the inlet pipe is opened now then the time in which the tank will be full is ………….min?