$($a$)$ Force of $=7+4($unit N$)$ is applied to displacement of $=3-4+2($unit m$).$ Find work $($unit J$).($b$)$ A particle of mass m $=2$ kg moves in the xy plane with a velocity of $=3+5($unit m$/$s$).$ Determine the angular momentum of the particle about the origin when its position vector is $=2+3($unit m$).$