Ramsay Travel offers helicopter service from suburban towns to John F$.$ Kennedy International Airport in New York City. Each of its thirteen helicopters makes between $900$ and $1,500$ round$-$trips per year. The records indicate that a helicopter that has made $900$ round$-$trips in the year incurs an average operating cost of $$750$ per round$-$trip, and one that has made $1,500$ round$-$trips in the year incurs an average operating cost of $$600$ per round$-$trip.

Read the requirements.

Requirement $1.$ Using the high$-$low method, estimate the linear relationship $y=a+bx,$ where $y$ is the total annual operating cost of a helicopter and $x$ is the number of round$-$trips it makes to JFK airport during the year.

$=+1$