A man phoned his daughter to ask her to buy a few things he needed for a trip. He told her she would find enough dollar bills for the purchases in an envelope on his desk. She found the envelope with 98 written on it.

In a store she bought $90 worth of things, but when it was time to pay she not only didn’t have $8 left over but she was short.

By how much was she short of cash, and why?