[ACE-OF-ACES]

Oh ok, thanks a bunch ACE-OF-ACES.

No prob!

The reverse works too

That is to say you want to know what altitude you can do 395mph at

Just this time start at the X axis, move your finger up until it reachs the green line, than move it left until you hit the Y axis, under your finger will be the altitude

Also note on some graphs there may be more than one altitude where you can reach that speed