An observer moves towards a stationary plane mirror at a speed of $4m{s}^{-1}$. With what speed will his image move towards him?

The correct option is C $8m{s}^{-1}$
$u=4m{s}^{-1};$
When an observer moves towards a stationary plane mirror at a speed of $4m{s}^{-1}$, his image would also be seen running towards him with a speed $2\times 4=8m{s}^{-1}$.