For the years from 2001-2010, the number of americans traveling to other countries by plane
can be represented by the polynomial function a(t) = 20t^4 – 428t^3 + 2760t^2 – 4320t + 33,600,
where a is the number of thousands of americans traveling abroad
by airplane and t is the number of years since 2001. in which year
were there 40,000,000 americans traveling abroad? use the
rational root theorem to find your answer.
(hint: consider the function's domain and range before finding all
possible rational roots.)