Three inlet pipes X, Y, and Z and one outlet pipe W are connected to a tank. Pipes X and Y together can fill a tank in 12 minutes, and pipes X and Z together can fill the tank in 10 minutes. If the ratio of efficiency of pipe Y to that of pipe W is 3:1 and the ratio of efficiency of pipe Z to that of pipe W is 4:1, then in what time pipe W alone can empty 75% of the fully filled tank?