A raindrop with radius R = 0.2 mm falls from a cloud at a height h = 2000 m above the ground. Assume that the drop is spherical throughout its fall and the force of buoyance may be neglected, then the terminal speed attained by the raindrop is :[Density of water fw = 1000 kg m$-3 and Density of air fa = 1.2 kg m-3, g = 10 m/s2, Coefficient of viscosity of air = 1.8 \times 10-5 Nsm-$2]