I need a bit of help with a problem. I am pretty sure I know what formula I should use, I just don't know how.

Question:

I think I need to use $\displaystyle (a_1 + a_2 + ... + a_n)^r = \Sigma \binom{r}{x_1 x_2 ... x_n} a^{x_1}_1 a^{x_2}_2 ... a^{x_n}_n$ but I am not sure. Any help would be great! I have already looked thought the book and there isn't any other problems of this sort that I can find, and this book does not have a students solution manual.Find the coefficient of $\displaystyle v^2w^4xz$ in the expansion of $\displaystyle (3v + 2w + x + y + z)^8$