Follow the steps below to evaluate the indefinite integral using the substitution method.

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}4x^3(x^4+5{)}^{8}dx$

a$.$ LET $u=$

b$.$ THEN $du=$

c$.$ SO$,$ the original integral, written in the variable $u$ is:

f $$