The $0\mathrm{.}5$m long uniform rigid steel bar shown in Figure Q$1$ has a mass of $720$g $.$ It is attached at point H to a hinge, which allows free rotation of the bar in the vertical $($x y$)$ plane. For the position shown in Figure Q$1,$ the bar is horizontal and has a constant angular velocity of $6$ rad $/$ s$.$ At this position, a moment of $5$ Nm is applied. For the instant the moment is applied, determine: a$)$ the angular acceleration of the bar; $[10$ marks$]$ b$)$ the reaction forces in the x and y directions at the hinge H$.[10$ marks$][$Note: the mass moment of inertia of a solid bar of length $/$ and mass m is given by: $.$I$\_$G$=$m l$^2/12]$