A golf instructor offers 1-hour private lessons from 2 pm to 6 pm every Saturday afternoon. His hourly rate is $60. The instructor takes appointments during the weekdays. Recently, the instructor receives quite a few late cancellations in Saturday morning. He can do nothing given the short notice. Therefore, the instructor institutes an overbooking policy. In case a customer cannot be served, the instructor will give a $40 certificate (he buys it from the golf club) for a free round of golf. The number of no-shows can be 1, 2, 3, or 4, each with a probability of 0.25. How many reservations should the instructor take