The $50-$kg block at A is mounted on rollers so that it moves along the fixed horizontal rail with negligible friction under the action of the constant $300-$N force in the cable. The block is released from rest at A$,$ with the spring to which it is attached extended an initial amount x$1=0\mathrm{.}233$ m$.$ The spring has a stiffness k$=80$ N$/$m$.$

$($a$)$ Draw a free body diagram of the system and determine the

work done by the spring acting on the block

$($b$)$ Calculate the velocity of the block as it reaches position $B$