Evaluate the following line integrals

$($a$){\displaystyle \underset{c}{\overset{\phantom{}}{}}}6xds$ where $C$ is the portion of $y=x^2$ from $x=-1$ to $x=2$

$($b$){\displaystyle \underset{c}{\overset{\phantom{}}{}}}{x}^{2}dy-yzdz$ where $C$ is the line segment from $(4,-1,2)$ to $(1,7,-1)$ is given by $r(t)=(t^3,1-3t,e^7)$