Help with a and b please

A cylindrical tank, shown to the right, has height 9 m and radius 1 m. a. If the tank is full of water, how much work is required to pump the water to the level of the top of the tank and 9 m out of the tank? Use 1000 kg/m" for the density of water and 9.8 m/s for the acceleration due to gravity. b. Is it true that it takes half as much work to pump the 1 m water out of the tank when it is half full as when it is full? Explain