$($a$)$ The $100-kg$ beam BD is supported by two rods having negligible mass. Determine the force developed in each rod if at the instant, $=30,=6ra\frac{d}{s}.$

$($b$)$ A uniform slender rod of length $L=900mm$ and mass $m=4kg$ is suspended from a hinge at C$.$ A horizontal force P of magnitude $75$ N is applied at end B $.$ Knowing that $r=225mm,$ determine $($a$)$ the angular acceleration of the rod, $($b$)$ the components of the reaction at C $.$