Loving on the Lawn_英语成人笑话

a man was walking one day, when he came to this big house in a nice neighbourhood.
suddenly he realised there was a couple making love out on the lawn. then he noticed another couple over behind a tree. then another couple behind some bushes by the house.
he walked up to the door of the house, and knocked. a well dressed woman answered the door, and the man asked what kind of a place this was.
"this is a brothel", replied the madam.
"well, what's all this out on the lawn?" queried the man.
"oh, we're having a yard sale today."