A tank has three inlets A, B and C and an outlet R. The outlet R takes 20 min to empty the full tank. The inlet B takes half time of A and twice the time than C. If the relation between B and R time is 2 ∶ 5, what is the time taken to fill the tank by all three inlets when outlet R is open?
1
3.2 min
2
4.67 min
3
2.58 min
4
3.56 min
5
4.98 min