You have ten fingers, right? Well, if you can't do your sums on ten fingers it's untenable. For example Ludlow was given money by his wife to pay for her Avon order but there's only enough money there to pay for nine beers and there are ten guys. Nine beers, ten guys...untenable.
What does Ludlow do? He has three beers with the girl selling Avon, she can't remember whether he paid or not for the stuff, he finishes off the last three beers and tells the wife the Bondo is beginning to work for her.
Untenable!
You are a master. A+++ ; )