A metal block of base area $0.20{\mathrm{m}}^2$ is placed on a table, as shown in figure. A liquid film of thickness 0.25 mm is inserted between the block and the table .The block is pushed by a horizontal force of 0.1 N and moves with a constant speed .If the viscosity of the liquid is $5.0\times {10}^{-3} \mathrm{PI}$, the speed of block is_______ $\times {10}^{-3}\mathrm{m}/\mathrm{s}$