Extra credit: Calculate the cost of handling a zero cost repair.
That's a repair job that requires zero time and materials to fix, but
still requires, handling, paperwork, overhead, and possibly shipping.
The last time I did that, based on 200 working daze per year and an 8
hr day, I needed to charge about $100 for a zero cost fix.

We are caught in a dilemma... If stuff is made to a high quality standard,
then it won't break down very often, and won't need the repair. But -- to
some degree -- we need stuff to break down to encourage people to buy new
technology, which appears at an ever-faster rate.