A cistern is fitted with many inlets and outlet taps. The empty cistern gets filled in 10 hours when 9 inlet and 5 outlet taps are opened. It takes 30 hours when 6 inlets and 5 outlets are opened. How much time does it take for the empty cistern to completely get filled if 2 inlets and 2 outlet taps are opened?
1
18.75 days
2
9.375 days
3
9 days
4
10.5 days