Homework H$\mathrm{.}2.$C

Given: Rigid body AB is shaped as quarter$-$circle arc with a radius of $R.$ End B of the bar is constrained to move along a vertical wall, whereas end A moves along an incline at an angle of $=53\mathrm{.}13$ with respect to the horizontal. At the instant shown, the center O of the AB arc is directly below end B $,$ and end A moves with a constant speed of $v_A.$

Find: For this problem:

$($a$)$ Determine the velocity and acceleration of end B of the bar. Express your answers as vectors and in terms of the parameters of $v_A$ and $R.$

$($b$)$ Is the speed of B increasing, decreasing or constant?