One end of a massless rope, which passes over a massless and frictionless pulley $P$ is tied to a hook $C$ while the other end is free. Maximum tension that the rope can bear is $360 \mathrm{~N}$. With what value of maximum safe acceleration (in $\mathrm{ms}^{-2}$ ) can a man of $60 \mathrm{~kg}$ climb on the rope?