1. [5 marks] A small regional airline's passenger traffic has been falling at a nearly linear rate. In 2011, there were 515, 000 passengers; in 2016, there were 475, 000. If n is the number of passengers carried by airline per year and t is the time in years (t = 0 in 2011), then:

(a) Determine the linear estimating function n = f(t).

(b) Interpret the slope's significance.

(c) What is the predicted number of riders by the year 2025?

(d) If passenger numbers drop below 379,000, the airline is expected to go out of business. According to your function in part (a), when will this happen?