Block B slides in the horizontal direction as it is pushed by the rod R$.$ The rod turns at angular speed $10$ rad$/$s in the clockwise direction about the pin. $($a$)$ find the velocity of the block when $=60.$ Also, if the angular acceleration of the bar is $40$ rad$/$s$2$ in the counterclockwise direction at the same instant of time, $($b$)$ find the acceleration of the block. $($Assume that the block is always in contact with the rod and that the rod is slender.$)$