The beam is supported by a pin at $A$, a roller at $B$, and a post having a diameter of $50 \mathrm{mm}$ at $C .$ Determine the support reactions at $A, B,$ and $C .$ The post and the beam are made of the same material having a modulus of elasticity $E=200 \mathrm{GPa},$ and the beam has a constant moment of inertia $I=255\left(10^{6}\right) \mathrm{mm}^{4}$.