Pumps A, B, and C each work at their own constant rate. When a certain tank is full, it takes pump A, operating alone, 3 hours to empty the tank; and it takes pump B, operating alone, 2 hours to empty the full tank. When the tank is empty, it takes pump C, operating alone, 6 hours to fill the tank. If all 3 pumps operate simultaneously, with pumps A and B emptying the tank and pump C filling it, how many minutes will it take to empty the tank if it is initially 1/2 full?
A. 30
B. 35
C. 40
D. 45
E. 50
A. 30
B. 35
C. 40
D. 45
E. 50
