What is the frictional force on a drum of radius $R$ and mass $M$ if it rolls down without slipping along an inclined plane of angle $\mathrm{\theta }$?

A sphere $S$ rolls without slipping, moving with a constant speed on a plank $P$. The friction between the upper surface of $P$ and the sphere is sufficient to prevent slipping, while the lower surface of $P$ is smooth and rests on the ground. Initially, $P$ is fixed to the ground by a pin $N$. If $N$ is suddenly removed,