Susan needs to be at class from 6 to 9 p.m. Demetri needs to be at a meeting from 6:30 to 8:30 the same night. They have only one car. If Demetri drops Susan off at class and picks her up, so both get to be where they need to be, and it works better for Susan not to have to park in a student parking lot far from the class, this solution could be called