Block A of mass $35 \mathrm{~kg}$ is resting on a frictionless floor. Another block B of mass $7 \mathrm{~kg}$ is resting on it as shown in the figure. The coefficient of friction between the blocks is 0.5 while kinetic friction is 0.4 . If a force of $100 \mathrm{~N}$ is applied to block $B$, the acceleration of the block $A$ will be $\left(\mathrm{g}=10 \mathrm{~m} \mathrm{~s}^{-2}\right)$: