Two blocks A and B of masses 4   kg and 6   kg are as shown in the figure. A horizontal force of…

Two blocks $A$ and $B$ of masses $4 \mathrm{kg}$ and $6 \mathrm{kg}$ are as shown in the figure. A horizontal force of $12 \mathrm{N}$ is required to make $A$ slip over $B$. Find the maximum horizontal force $F_B$ that can be applied on $B$ so that both $A$ and $B$ move together. (take $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)