scheduling 101

I LOVE scheduling. It's so much better than actually doing things. I just got the awesomest scheduling problem ever: there are two research assistants with their own class schedules, two lists of 45 research volunteers, and one sound booth (which is sometimes used by other people.) The experiment takes about 30 minutes but maybe more. What is the most efficient way to schedule the research subjects?

I'm not sure if I got the answer right, but what we did was each take two lab sessions a week, divide them up into 45-minute slots, and have the subjects email us with their three favorite slots. Then the person whose day is their first choice is in charge of emailing them back.

I think there should be an organizing class in high school. It would cover money, food, and time, the three most schedule-needing things in adult life. (There's probably an equation where [money = time] and [food = money*3] or [food = money+time]). This would be the homework:

1. Money: Suppose you forget to pay your rent 1 out of every 4 months, incurring a late fee of $5. If rent is $500 and you earn 3% interest, is it better to pay your rent 20 days early and never forget, losing interest, or to pay the late fee every 4 months?

2. Food: If you go through a gallon of soy milk per week and 1.5 boxes of cereal per week, and you currently have 0.25 gallons of soy milk and 1 box of cereal, and it's Wednesday, which day will you have to go to the store?

3. Time: If last bus of the day sometimes stops halfway to your house and sometimes goes all the way, and walking takes 30 minutes but the bus all the way takes 15, and you wait for the bus an average of 5 minutes, what fraction of days does the bus have to refuse to take you all the way before it becomes more worth your while to just walk?