If curl vec$(F)=(x^2+z^2)vec(j)+8$vec$(k),$ find ${\displaystyle \underset{C}{\overset{\phantom{}}{}}}$vec$(F)*dvec(r),$ where $C$ is a circle of radius $3,$ centered at the origin, with

$($a$)C$ in the $xy-$plane, oriented counterclockwise when viewed from above.

${\displaystyle \underset{C}{\overset{\phantom{}}{}}}$vec$(F)*dvec(r)=$

$($b$)C$ in the $xz-$plane, oriented counterclockwise when viewed from the positive $y-$axis.

${\displaystyle \underset{C}{\overset{\phantom{}}{}}}$vec$(F)*dvec(r)=$