Apparently I did not keep my textbook, and don't remember which one I had.

This one[1] is probably decent (looking at its table of contents):

https://www.amazon.com/Engineering-Economic-Analysis-Donald-...

It's not a sophisticated topic. If you're a non-CS engineer who knows calculus and algebra well, this is one of the easiest topics in the curriculum.

Even if your calculus is poor, simply using the concepts with a spreadsheet will get you almost all the way.