Ramone Travel offers helicopter service from suburban towns to John F. Kennedy International Airport in New York City. Each of its 11 helicopters makes between 1,000 and 2,000 round-trips per year. The records indicate that a helicopter that has made 1,000 round-trips in the year incurs an average operating cost of $350 per round-trip, and one that has made 2,000 round-trips in the year incurs an average operating cost of $300 per round-trip. Using the high-low methods, estimate the linear relationship y=a + bx, where y is the total annual operating cost and x is number of round trip.