please explain

A full water tank in the shape of an inverted right circular cone is 20 m across the top and 10 m high. If the surface of the water in the tank is 2 m below the top of the tank, how much work is required to pump all the water over the top of the tank? (The density of water is 1000 kg/m', use acceleration due to gravity g - 9.8 N/kg.) (Use symbolic notation and fractions where needed.)