A cashier scans the customers 15% coupon and the customer doubts it’s correct. So the cashier does the math on a calculator and gets the same answer.  Of course customer still disagrees with the cashier and asks for a manager.  So the manager arrives and also comes up with the same answer, so finally the customer accepts it, but…  On their way out they make a comment to the manager that the cashier should know how to do their job better.  So a computer and two people all give them the same answer and yet they were still believe their correct in their ass(u)mptions?   Must be nice to always be right and know it.