I am trying to create two functions but I am having trouble. The first consists of converting degrees Fahrenheit to Kelvin using this formula `(F - 32)*(5/9) + 273` and another calculates the cricket chirping rate (in `s^-1`) using Dolbear's law which is `Tf=40+N15` where `Tf` is the temperature in degrees Fahrenheit and `N15` is the rate of chirps per minute.

I was able to make the temperature function.

    f[F_] = (F - 32)*(5/9) + 273

I am just having trouble with the second function.