Add three forces, vec$(A),$vec$(B),$ and vec$(C),$ in above figure $($not in scale$)$ with given $a=5ft,b=6ft,c=4ft,$

$|vec(A)|=20lb,|vec(B)|=70\mathrm{.}1992lb,$ and $|vec(C)|=105lb$

$i+$

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}j+$

$k$ lb