Torque and angular acceleration: A board of length $2d=6\mathrm{.}5m$ rests on a cylinder $($the "pivot"$).$ A ball of mass $6$ kg is placed on the end of the board, which has a mass of $10$ kg $.$ The figure shows the objects at a particular instant.

$($a$)$ Let the point at which the board touches the cylinder be location $A.$ At that moment, what is the torque vec$()$ about location $A$ in vector form? $(8$ points$)$

$($b$)$ At that moment, what is the angular acceleration vec$()$ in vector form of the board $+$ ball system? $(8$ points$)$