Customers arrive to a concession stand at the rate of 72 per hour. Arrival rate can be described by a Poisson distribution. The stand has 4 windows. Buying a hot dog takes on average 3 minutes per customer and varies exponentially. What is the maximum waiting-line length (at least) 40% of the time

Out of the 150 students at a summer camp, 72 signed up for canoeing. there were 23 students who signed up for trekking, and 13 of those students also signed up for canoeing. use a two-way table to organize the information and answer the following question: approximately what percentage of students signed up for neither canoeing nor trekking?