check the picture below.
that's done just with the provided links, and I simply ran a line, so it'll be thereabouts, roughly between 13 and 14, depending on how you hang the line.
anyhow, if you have a TI(texas instruments) 89+ or higher, you can just provide the value pairs of the data and run a quadratic regression, or an exponential.
there are some online regression calculators as well.
