To calculate the rate of change or slope between two points, we use the formula:
slope = (change in y) / (change in x)
In this case, the initial gas price in 2001 is $1.75, and twelve years later in 2013, the gas price is $4.35. So, the change in y (change in gas price) is 4.35 - 1.75 = $2.60. The change in x (change in years) is 2013 - 2001 = 12 years.
Now we can calculate the slope:
slope = (change in y) / (change in x) = 2.60 / 12 = 0.2167
Therefore, the rate of change or slope between the two points is approximately 0.2167, or 21.67%.