Using appropriate FBDs$,$ work problem $2\mathrm{.}2-17$ from the textbook, which is as follows. The three$-$member frame structure in the figure is subjected to a horizontal load $P=500lb$ at pin $C.$ The pins at $B,C,$ and $D$ apply axial loads to members $BD$ and $CD.$ If the stresses in members $BD$ and $CD$ are ${}_1=1200p$ si and ${}_2=-820p$ si$,$ what are the respective cross$-$sectional areas of the two members?