C15. A block of mass $m$ sits on top of an identical block which rests on a flat rough table. The coefficient of static friction between the block surfaces is $\mu_1$ and between the lower block and the table is $\mu_2$.

If $m = 5\,\text{kg}$, $\mu_1 = 0.6$, and $\mu_2 = 0.2$, the minimum force applied on the top block to induce motion in the system of blocks is (take $g = 10\,\text{m/s}^2$)