Rigid Body Kinetics Homework Help - Solving Equations & Finding Answer

[aolse9]

Homework Statement

Homework Equations

$$\Sigma$$M = I$$\alpha$$
$$\Sigma$$F = ma

The Attempt at a Solution

I have made an attempt at this problem, it can be seen in the image below. I think I have done everything correctly, but my answer is incorrect. Any help would be greatly appreciated.

 

[aolse9]

Any ideas?

 

[aolse9]

...no ideas. Come on guys I'm running out of time!