A.B AND C are three pipes such that a and b are inlet ones and can fill a tank in 12 and 6 mins . C is a pipe which can work either as an inlet or as an outlet pipe taking 24 mins to fill or emty as the case may be. If C and A and C and B wok alternatively for 1 min each .The tank gets filled in 10 mins.Find the time for which the C work as an outlet