I wouldn't have spent more time, and I was serious. I had done a lot of similar work for a different call center in the late 90s so I knew my model worked. I did it in Excel because I remembered the calculations but I'd forgotten how to code in whatever it was we used back then. (Now I can't even remember what it was we used. I think it was Lotus 1-2-3, maybe. I'm getting old.)

The other person's model used a different approach to the problem, using variables that I completely ignored. Turns out he had been sweating over this problem for a couple of weeks, googling for methods and models and massaging some complicated VBA program he'd built. (He loved VBA, go figure.)

When he got to his answer, I said, "OK, now add 10%." He exploded, "That's what drives me nuts about this! Every paper takes you through all this complicated math and detailed calculations, then at the end they say, 'Add 10%'! What the hell!?"