Mr: Bakkari's Huge Water Tank

Once Upon A Time , There Was a Huge Water tank on Mr : Bakkri's House Roof , Mr Bakkari is someone who is Very interested in Calculations , also he love physics , he learned in physics how to calculate the speed of Streamed Water Between 2 Pumping Pipes or more and learned how to Calculate the Total time taken the water being streamed From An Edge Of a plumping Pipe To Another One , But Mr : Bakkari Is Now 60 years Old And He is suffering from amnesia but he Still has a nice strong eyes , He can see as a child aged 20 years , He want to make some calculations on his Water Tank. So , He has to wait for his son Fakhry , who is a university student at The Faculty of Computer Science , his son loves math very much , Fakhry has a nice physics course at his university but he doesn't learned about liquid streaming Except one time in his High School , Mr : Bakkari hope that his son will help him solve his problem , He thought that his son is learning these problems in his Faculty .. but he is Also believing that his son is Thinking like a mathematician Because of his Computer Sciences studies which make persons smart people , He wonders that his son will make an Algorithm to solve his problem , But Unfortunately , his son will do a project with his friends tonight and he will be back at the Crack of dawn . Thus, Mr:Bakkari is asking you to help him solve his problem .. Mr:Bakkri's Water Tank has 2 taps , one for putting water in it , and the other one is To Empty it again , the first one fills the Whole Water tank in 3 hours and the other one empty it in 4 hours , What is the factor that will be multiplied with the Full Volume to Get the Water tank Filled in Time Equal to One Hour ?

Note :: In The Choices You Will See (Hours) , Omit and replace them With (Of the Full Tank) .. Sorry About This Mistake.