Spherical Yo-Yo

A spherical yo-yo is released from rest on a string of length $L$ meter as shown. The spindle of the yo-yo has a radius of $r$ and the radius of the yo-yo itself is $R > r$. The yo-yo has a mass $M$ grams and for the purposes of this problem has the moment of inertia of the sphere, $I = \frac{2}{5}MR^2$.

a) Find the acceleration of the center of mass of the yo-yo.

b) Find the angular momentum of the yo-yo when it reaches the bottom of the string.