She opened her purse and put in 50 cents, studied the machine a short while, pushed a Diet Coke selection, and out came a Diet Coke. She placed it on a counter next to the machine.
Then she reached in her purse again and pulled out a dollar and inserted it in the machine. Studying the machine carefully, she pushed the button for Coke Classic and out came a Coke Classic and 50 cents change.

She immediately took the 50 cents and put it in the machine, studied it for a moment and pushed the Mountain Dew button. Out came a Mountain Dew. She placed them both on the counter next to the Diet Coke.

As she was reaching into her purse again, the business man, who'd been waiting patiently for several minutes by then, spoke up. "Excuse me, miss, but are you done yet?"
She looked at him and indignantly asked, "Well Duh! Can't you see I'm still winning"