ANS:B - 2^3/2

The power required by a centrifugal pump is directly proportional to the head and the flow rate. When the head is doubled, the power required by the pump increases by the cube of the ratio of the new head to the original head. So, if the head is doubled, the ratio of new head to original head is 2:12:1, and the power required will increase in the ratio of 2^3=8:1 Therefore, the correct answer is: 8/1=8