A swimming pool is 49 units long, 7 units wide, 1 units deep at the shallow end and 8 units deep at the deep end. Water is being pumped into the pool at 1/3 cubic units per minute and the height of the body of water is 1 unit at the deep end.

a) What percentage of the pool is filled when there is 1 unit of water at the deep end?

b) At what rate is the water level rising if the height is less than or equal to 7?