Ineed to calculate the rate of change for the time periods and place them in order from lowest rate of change to highest rate of change

1950 - 1980 : 
(1950,257.4)(1980,909.0)
slope(rate of change) = (909.0 - 257.4) / (1980 - 1950) = 651.6 / 30 = 21.72 mill

1950 - 2010
(1950,257.4)(2010,14,456.3)
slope = (14,456.3 - 257.4) / (2010 - 1950) = 14198.9 / 60 = 236.65 mill

1970 - 1980
(1970,380.9)(1980,909.0)
slope = (909.0 - 380.9) / (1980 - 1970) = 528.1 / 10 = 52.81 mill

1980 - 2010
(1980,909.0)(2010,14456.3)
slope = (14,456.3 - 909.0) / (2010 - 1980) = 13547.3 / 30 = 451.58 mill

1990 - 2000
(1990,3206.3)(2000,5628.7) 
slope = (5628.7 - 3206.3) / (2000 - 1990) = 2422.4 / 10 = 242.24 mill

order from lowest to highest :
(1) 1950 - 1980
(2) 1970 - 1980
(3) 1950 - 2010
(4) 1990 - 2000
(5) 1980 - 2010