Two announcers are used to read names at the semiannual commencement exercises held at a regional university in America's heartland. All students have their names read then walk briskly to the president who shakes their hand and offers them an empty diploma cover until such time that all financial obligations to the university have been met. The president greets about $900$ students in an eight hour day. The diploma covers come in boxes of $12$ and it takes one hour to carry one from the receiving dock to the field house where the ceremony is held. The president likes to keep things moving, so he has requested a $50\%$ safety factor How many containers are needed?