Question

Two pipes X and Y can fill an empty tank in 8 hours and 10 hours, respectively. Pipe Z alone can empty the completely filled tank in 15 hours. Firstly, both pipes X and Y are opened, and after 4 hours, pipe Z is also opened. What will be the total time (in hours) required to completely fill the tank?

A 89/29
B 89/19
C 88/19
D 88/29
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