One morning, Lisa and Sadie decided to go out for breakfast. The waitress told them that the special that morning was two eggs, tomatoes, mushrooms, hash browns and toast for £3.99.

"That sounds good," said Sadie, "but I don't want the eggs."

"OK," said the waitress, but I will then have to charge you £4.50."

"Why," asked Lisa, "it doesn’t make sense.

"Because you will then in effect be ordering a la carte," the waitress replied.

"Do you mean I'll have to pay for not taking the eggs?" Sadie asked.

"Yes," replied the waitress.

"OK then, I'll take the special," says Sadie.

"How do you want your eggs done?" asked the waitress.

"Raw and in the shell," Sadie replied.

At the end of the meal, Sadie took the two eggs home.