A drop of water of radius $0.0015 \,mm$ is falling in air. If the coefficient of viscosity of air is $2.0 \times 10^{-5} \,kg / ms$, the terminal velocity of the drop will be
(The density of water $=1.0 \times 10\, kg / m ^{3}$ and $g=10\, m / s ^{2}$ )