2kg block is kept on 1kg block as shown. Both blocks are initially at rest. The friction between 1 kg block and fixed surface is absent and the coefficient of friction between 2kg block and 1kg block is $\mu =0.1.$ A constant horizontal force $\mathrm{F}=4 \mathrm{N}$ is applied on 1kg block. If the work done by the friction on 1kg block in 2s is $– \mathrm{XJ}$, then find the value of $\mathrm{X}$. $\mathrm{g}=10\mathrm{m}/{\sec }^2$