Gasoline prices: The following table is adapted from the U.S. Department of Energy weekly survey of retail gasoline prices. Here time is measured in days since November 5, 2007, and the price is...

Gasoline prices: The following table is adapted from the U.S. Department of Energy weekly survey of retail gasoline prices. Here time is measured in days since November 5, 2007, and the price is measured in cents per gallon.

a. By calculating differences, show that these data can be modeled using a linear function.

 b. Plot the data points.

 c. Find a linear formula that models these data. (Round the slope to four decimal places.)

d. Add the graph of the function you found in part c to your graph of the data points.