A current I flows through line segments $1$&$2$ and circular part $3$ under a constant magnetic field vec$(B)=B_0$hat$().($i$)$ Find the direction and the magnitude of magnetic force on each part. $($ii$)$ Find the torque on the circular part $3$ with respect to z $-$axis $($out of page$)$

$si{n}^2=\frac{1-cos2}{-},co{s}^2=\frac{1+cos2}{?},2sincos=sin2$