We are to determine the rate in cubic meters per minute at which water is flowing into a swimming pool with a rectangular base.
1. Volume of swimming pool is 420sq.mm
Not sufficient. We need the length of time it takes to fill the pool in order to determine the rate in cubic meters per minute. Since that information is not available, we cannot determine the rate.
2. Surface level of the water rises at 0.5m per minute.
Not sufficient because we need the surface area of the base of the pool in order to determine the rate in cubic meter per minute given the rate at which the surface level rises.
1+2
Still not sufficient. We still do not know the time it takes to fill the pool, so even though we know the volume, we can't determine the rate in cubic meters per minute. In a similar vein, we still do not know the surface area of the pool which would help in determining the rate in terms of volume per minute given the rate at which the water level rises in the pool.
The answer is E in my view.