A rain drop off radius 2mm falls from a height of 500m above the ground. It falls with decreasing acceleration due to resistance of air until at half it's original height, it attains it's maximum speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of it's journey? What is the work done by the resistive force in the entire journey if it's speed on reaching the ground is 10m/sec.