A small sphere of mass m is launched horizontally over a bod…

A small sphere of mass m is launched horizontally over a body of water from a height h above the water and with a launch speed v0. Assume that the only force acting on the projectile after launch is gravity and that the point of zero gravitational potential energy is water level. What is the amount of work done by gravity on the projectile during its flight (from right after launch to the time it hits the water)?