The cost of mailing a letter increased 40¢ from 1958 to 2011. The table below lists the cost of a first-class stamp in selected years.
Year, x First-Class Postage
Cost C (in cents)
1958, 0 ................................ 4¢
1968, 10 ................................ 6
1978, 20 .............................. 15
1988, 30 .............................. 25
1995, 37 .............................. 32
2002, 44 .............................. 37
2006, 48 .............................. 39
2008, 50 .............................. 42
2011, 53 .............................. 44
a) Use a graphing calculator to fit an exponential function to the data, where x is the number of years after 1958.
b) Graph the function with a scatter plot of the data.
c) Estimate the cost of a first-class stamp in 1970, in 2000, and in 2015.