I'm having a fight with a coworker. I'm 1000% right but I need confirmation.

If you go to a restaurant and you get a discount off your bill, do you tip based on the original cost or the discounted cost?

the original amount
83.9%
the discounted amount
16.1%
Poll ended at .
@Firr
The original amount- which also happens to be how the % tip calculators built into most online food apps do it too.