Three blocks are arranged on a horizontal table $\mathrm{ABCD}$ as shown in the figure. The strings and pulleys are massless and both the pulleys stand vertical. The strings connecting blocks ${\mathrm{m}}_1$ and ${\mathrm{m}}_2$ are also vertical and are perpendicular to faces $\mathrm{AB}$ and $\mathrm{BC}$ which are mutually perpendicular to each other. If ${\mathrm{m}}_1$ and ${\mathrm{m}}_2$ are $3 \mathrm{kg}$ and $4 \mathrm{kg}$ respectively. Coefficient of friction between the block ${\mathrm{m}}_3=10 \mathrm{kg}$  and the surface is $\mathrm{\mu }=0.6$ then, frictional force on ${\mathrm{m}}_3$ is