Across the United States, there are approximately 45,000 flights each day. In a certain simulation, the total number of flights that have begun across the United States n hours since midnight on a given day can be modeled using an arithmetic
sequence, where 12:00AM is represented by n = 0. The total number of flights that had begun by 5AM that day was
11,750, and by 11AM there had been a total of 22,250 flights that had begun. Based on the simulation, how many total flights had begun across the United States by 6PM that day?