Evaluate the line integrals:

$a.{\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}x{y}^{4}ds$;$Cis$ the plane curve that $is$ the right half $of$

the circle $x^2+y^2=16$

$b.,{\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}xy{e}^{yz}dy$;$Cis$ the space curve given $by$

$x=t,y=t^2,z=t^3,0t1$