What is the work done by the resistive force on a raindrop of radius 2 mm that falls from a height of 500 m above the ground? It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. If its speed on reaching the ground is 10 m/s, what is the work done by the resistive force?