A tank can be filled by pipe A in 30 minutes and by pipe B in 24 minutes. Outlet pipe C can empty the full tank in X minutes.
If the tank is empty initially and if all the three pipes A, B and C are opened simultaneously, the tank will NEVER be full. Give the maximal possible value of X.

• Maximum possible value is 13 minutes and 20 seconds.
  
  Together, A and B fills the tank in 13 minutes and 20 seconds. If X is larger than this value, the tank would fill up in a matter of time.
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