A block of mass $2\ \text{kg}$ is held against a rough vertical wall by a horizontal force F, as shown in the figure. The coefficient of static friction between the block and the wall is $0.5$, and $g = 10\ \text{m/s}^2$. The smallest F that keeps the block from slipping down, and the friction force on the block when F is $60\ \text{N}$, are

Fig. 1: A 2 kg block pressed against a rough vertical wall by a horizontal force F; the coefficient of friction is 0.5.