$3.[2$op$].$ A horizontal rigid bar AD is supported by a pin at end A$,$ and two vertical elasticplastic cables, $BE$ and CF of same material and cross section area, $A=12m{m}^2.$ The length of cables BE and CF are $1$ m and $1\mathrm{.}2$ m $($unloaded$).$ The load, $P$ is applied slowly until both cables begin yielding $(($:${}_Y=1{10}^{-3},{}_Y=40$MPa PREVIOUS SOLUTION NEVER FOUND DISPLACEMENT IF POINT D$.$