The dollars per capita of federal tax burden T can be described by
T = 2.11x3- 93.01x2 + 1373.9x + 394
where x is the number of years past 1990.
(a) Graph this function for values of x that correspond to the years 1990 to 2018.
(b) Is the graph increasing or decreasing over these years? What does this tell us about the per capita federal tax burden?