$4\mathrm{.}22$ Part $($a$)$ only. Solution not in back of book: $D_x=0,D_y=-20lb,D_M=20lb-ft.$

$4\mathrm{.}22$ Beam $AD$ carries the two $40-lb$ loads shown. The beam is held by a fixed support at $D$ and by the cable $BE$ that is attached to the counterweight $W.$ Determine the reaction at $D$ when $(a)W=100Ib,(b)W=90Ib.$

Fig. P$4\mathrm{.}22$ and P$4\mathrm{.}23$