Mrs. Green was the manager of a large company and she frequently had to have meetings with other business people in a room in her building. She did not smoke at all, but many of the other people at the meetings did, so she often found the air during the meetings terrible.

One day,after an hour, her throat and eyes were sore and she was coughing a lot, so she called a big air conditioning company and asked them to work out how much it would cost to keep the air of the meeting room in her building really clean.

After a few days the air conditioning  company sent  in two estimates for Mrs. Green to choose from. One estimate was for $5,000 to put in new air conditioning, and the other was for $5.00 for a sign which said, NO SMOKING.

格林太太是一家大公司的经理，必须经常在她大厦内的房间跟其他的生意人开会。 她本人不抽烟，但是许多其他来开会的人却抽烟，所以她常常觉得会场里的空气令人难受。

有一天，开了一小时的会，她喉咙和眼晴都很痛，而且咳口嗽得很厉害，所以她就请了一家处理空气调节的大公司，请他们计算一下要花多少钱，才能使大厦会议室内的空气保持绝对干净。

几天后受理空气调节的公司开了两张估价单供格林太太选择。 一张是花五千元来安置新的空气调节设备，另一张是花五块钱买一个“请勿抽烟”的牌子。