The goal here is to find the slope, so we have to use the slope formula.
Slope formula: Change in y's/ Change in x's
Your "Y" in this scenario would be the years and the "X" would be the cost in a certian year.
So, 2013 - 2003 / 630 - 551 = 10 / 79 = .79
$0.79 per year increase.
