Students Arrive at a University Business Library During Peak Evening

Multiple Choice

Students arrive at a university business library during peak evening hours at a rate of 40 students every half hour. A periodic count shows that there are 200 students in the library at any one time. On average, how long is each student's stay in the library?

A) less than or equal to one hour
B) greater than 1.0 but less than or equal to 2.0 hours
C) greater than 2.0 but less than or equal to 3.0 hours
D) greater than 3.0 hours