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Pump A can empty a pool in A minutes, and pump B can empty the same pool in B minutes. Pump A begins emptying the pool for 1 minute before pump B joins. Beginning from the time pump A starts, how many minutes will it take to empty the pool?
A.A+B−12
B.AB+1A+B
C.ABA+B
D.ABA+B−1
E.AB−1A+B
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