On a very hot day my friend pulled into a service station and bought a couple six-packs of beer.  While leaving he noticed a model-type blonde pumping gas. It was so hot she had unbottoned her blouse down to her waist and had her boobs just hanging out.

After she finished pumping gas she walked by my friend's car and noticed the beer on his front seat. She leaned in the window and said in a sultry voice, "I am a firm believer in the barter system. I would be willing to trade sex for beer."

My friend sat back and thought for a moment then said, "So, what kind of beer do you have?"