$(8)$ Evaluate by changing the order of integration $($a$)$Ma$){\displaystyle \underset{0}{\overset{3}{}}}{\displaystyle \underset{\sqrt[\phantom{2}]{\frac{x}{3}}}{\overset{1}{}}}{e}^{y^3}dydx$

$($b$){\displaystyle \underset{0}{\overset{1}{}}}{\displaystyle \underset{0}{\overset{1}{}}}{\displaystyle \underset{x^2}{\overset{1}{}}}12xz{e}^{z{y}^2}dydxdz$