Evaluate the indefinite integrals using Substitution. (use $C$ for the constant of integration.)

a) $\displaystyle \int 3x^{2}\!\left(x^{3}+8\right)^{8} \, dx =$

b) $\displaystyle \int \left(2x-9\right)\!\left(x^{2}-9x-2\right)^{7} \, dx =$

c) $\displaystyle \int x\!\left(x^{2}+7\right)^{7} \, dx =$

d) $\displaystyle \int \left(14-20x\right)\!\left(7x-5x^{2}+8\right)^{6} \, dx =$