" working girls and boys "

 "I wonder, though, whether the people who administer this university thought their choices through. The extra 20 minutes (the walks to/from the garage) are a fixed cost of people's daily commutes. This additional fixed cost gives them a disincentive to come into the office each day, and an incentive to try bunching their appointments, teaching, and office hours on fewer days to spread the fixed costs."

http://freakonomics.blogs.nytimes.com/2008/05/20/football-sex-and-parking/