A water drop of radius 1 $\mum falls in a situation where the effect of buoyant force is negligible. Co-efficient of viscosity of air is 1.8 \times 10-5 Nsm-2 and its density is negligible as compared to that of water 106 gm-3. Terminal velocity of the water drop is :
(Take acceleration due to gravity = 10 ms-$2)