ANSWER: B
EXPLANATION:
Perimeter = L + L + W + W
Perimeter = 12 + 12 + 5 + 5
Perimeter = 34
Since you have the whole surface area of the cube, you just divide 150 by 6, for each face
So the answer is 25 for one face of the cube.
The first pump empties half the pond in 3 hours, so in 1/6 that time (1/2 hour), it empties (1/6)·(1/2) = 1/12 of the pond.
The second pump empties the other 5/12 of the pond in that half hour, so has a pumping rate of (1/2 h)/(5/12 pond) = (6/5 h)/pond.
The second pump could do the entire job alone in 1 hour and 12 minutes.
