$4($Average$)$ Three forces of $20N$ each are applied to a triangular object as shown. The object is shaped as an equilateral triangle with sides one meter long.

$($a$)$ Calculate the resultant torque about the point A$.$ Ans: $-27\mathrm{.}3Nm,$

$($b$)$ Calculate the resultant torque about the point B$.$

Ans: $+7\mathrm{.}32Nm.$