I would say a certain amount of ratios is involved here.  You take 1 minute to load 2 bales, so if she has hooters as big as bales, you get to look at both for 1 minute.  If she has 'em as big as half a bale, you get 2 minutes.   See where I am heading here?  Take a tenth of a bale size and it is 10 minutes, anything else, she just has to go home topless when ever you are through.

Forgot to add, if you get her to ride the horse like Lady Godiva, you will owe her change, like maybe a thong shot.  OUCH! OUCH!  BRAIN FRIED AGAIN!!!!