$(27$ points$)$ The rigid beam BCD is subjected to the loadings shown and is supported by a double$-$sheared pin at $C$ and a link $AB.$ Determine the reactions at pin $C$ and member $AB.$ If the failure normal stress is $36$ MPa and the failure shear stress is $9$ MPa $,$ determine the minimum required diameter of pin C $,$ to the nearest mm $,$ and the minimum required diameter of member $AB,$ to the nearest mm $,$ if the factor of safety is $3.$

$FBD?$