You have two friends who want to find the average number of hours they sleep per night, over the course of a month $(30$ days$).$

Alice uses the following algorithm: Each morning, she records the number of hours she slept the prior night. At the end of $30$ days, she adds up all of the numbers that she recorded, and then divides the result by $30.$

Bob uses the following algorithm: he starts with a total of $0.$ Each morning, he adds the number of hours he slept the prior night to his current total, to get the new total. $($In other words, he keeps a running total of the number of hours of sleep so far in the month$).$ At the end of the $30$ days, he divides the running total by $30.$

Both of these algorithms will indeed give the average number of hours slept over the course of the month. Please explain why Alice might prefer her algorithm, and why Bob might prefer his. That is$,$ what are the benefits and drawbacks of these two algorithms?