mostly these are pretty easy to figure out, but I'm confused on this one.

Given the following, find the standard equation of the hyperbola

foci: (0, +/-8)

asymptotes: y=+/-4x

From the foci, I know the origin is at 0,0 and that it's vertical, which gives me

$\displaystyle \frac{y^2}{a^2} - \frac{x^2}{b^2}$

I also know that $\displaystyle c^2 = a^2 + b^2$, and, from the asymptote, I know that the ratio of rise to run is 4:1, so a=4b

I'm not really sure how to proceed from here, though. Can someone point me in the right direction please?

*edit*

forgot to add that, from the foci, I know that c=8. Still not sure how to proceed.