Problem $3$: A Mario platform, $m=20\mathrm{.}0kg,$ is supported by two weightless rods, as shown. At the moment, the

platform is at rest, but it will fall from this position $($rotating downwards$).$

$($a$)$ Determine the acceleration of the center of mass of the platform.

$($b$)$ Determine the support forces at A and B$.$

Note: you may not use all the dimensions shown in the figure.