Pipe Q and Pipe R together can fill a tank in 25 minutes. With Pipe S, all three pipes can fill the tank in 30 minutes. Pipe Q and Pipe T together can fill the tank in 30 minutes. Pipe S and Pipe T together can fill the tank in 75 minutes. Pipe R, Pipe S and Pipe U together can fill the tank in 75/4 minutes. Quantity I : Pipe R is opened for 15 minutes and then closed. Find the time taken by Pipe T to fill the remaining part of the tank.  Quantity II : Pipe Q is opened for 10 minutes and then closed. Find the time taken by Pipe S to empty the filled part of the tank. Quantity III : Find the time taken by Pipe Q, Pipe S and Pipe U to fill the tank.