This may seem elementary, but……. I’m elementary! 🤣🤣

I have a Vortex Viper HST 6-24x50 scope. It’s 2nd focal plane. When the scope is dialed to 18x power, the subtensions (hashes) are at true MOA value.

How do I determine what my yardages are when I’m dialed all the way in at 24x power? I want to have a chart printed out for my gun so that I can have it handy for “on the fly” yardages when dialed all the way in.

Thanks in advance!