Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is:
Correct answer C. 14
Correct answer C. 14
Tip: press A, B, C or D to answer, and N for the next question.
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