Maximum frictional force on a block of mass $20 \mathrm{kg}$ being pulled horizontally on a rough horizontal surface is $(\mu =0.1)$

A block of mass $10 \mathrm{kg}$ is kept on a fixed rough $(\mu =0.8)$ inclined plane of angle of inclination $30°.$ The frictional force acting on the block is

A block of mass $10 \mathrm{kg},$ moving with acceleration $2 \mathrm{m} {\mathrm{s}}^{-2}$ on horizontal rough surface is shown in figure

The value of coefficient of kinetic friction is