Still Good

Waiter: Here's the menu.

Customer: Thanks. Can I have a salad, please?

Waiter: Sure. And to drink?

Customer: One orange juice.

Waiter: Okay. Anything else?

Customer: No, that's all. How much is it?

Waiter: Four pounds. The salad is free today.

Customer: Free? Why?

Waiter: It's old. But it's still good!