A ROLLING BLOCK!!!

An empty cylinder with mass $M$ is rolling without slipping along a slanted surface whose angle of inclination IS $\alpha= 45°$ .

On an inner surface can slide freely a small block of mass $m=M/2$ . What is the angle $\beta$ between the normal to the slanted surface and the straight line segment connecting the centre of the cylinder and the block. Your comes to be in the form of

$arctan(a/b)$ .

Find $a+b$ .