A pump will fill a tank in 3 hours. Because of a leak in the tank, it took 3 hours 30 min to fill the tank. In what time the leak can drain out all the water of the tank and will make tank empty ?	Choose the correct choice from the following:
A) 20 hrs
B) 21 hrs
C) 22 hrs
D) 23 hrs
E) 24 hrs
work done for 1 hr without leak = 1/3   work done with leak = 31/2 ==&gt;7/2   work and leak in 1 hr = 2/7   work leak in 1 hr = 1/3 - 2/7 = 1/21   so 21 hrs   ANSWER 21 hrs
<result>B</result>
A pump will fill a tank in 3 hours. Because of a leak in the tank, it took 3 hours 30 min to fill the tank. In what time the leak can drain out all the water of the tank and will make tank empty ?