Q$\mathrm{.}3)$ The L$-$frame in figure below supports forces from two cables. Cable "EAD" passes through a frictionless ring at point $"$A$",$ and cable "OCG" passes through a frictionless ring at point $"$C$".$ The force in cable "EAD" is $800lb$ and the force in cable "OCG" is $400lb.$ For the cable forces applied at points $"$A$"$ and $"$C$",$ using the vector approach determine:

a$)$ the moment about point $"$B$",$

b$)$ the moment about point $"$A$",$ and c$)$ the moment about point $"$O$".$