A $196\mathrm{.}2N$ cubical block, having $20cm$ edge, slides down an inclined plane making an angle of $20$ with the horizontal on which there is a thin film of oil having a viscosity of ${2\mathrm{.}16}^{**}{10}^{3}N\frac{s}{m^2}.$ What terminal velocity the block will attain, if the film thickness is estimated to be $0\mathrm{.}025mm?$