A local restaurant has 28 tables that can each seat a party of up to four people. The restaurant does not take reservations. Parties arrive at a rate of 16 per hour and on average a party uses a table for 90 minutes (For simplicity assume that all parties have up to four people). If no tables are available, customers wait in the bar. What is the probability that an arriving party waits for less than 15 minutes before getting seated? (You can assume there is enough space in bar for customers to wait, and customers are willing to wait as long as it takes)