Forty years ago, a gallon of gas cost $1.20. Today, a gallon of gas costs 2.60. Suppose that the gas price increase has been entirely due to inflation. a. Calculate the annual inflation rate. b. Today, you plan to make a cash purchase for a new car. The Model K costs $24,000 and you estimate the car will last 10 years and require 600 gallons per year. The Model M costs $28,000 but gets better mileage, so it will only require 400 gallons per year. The cars are identical in all other respects, and they will both be worthless after 10 years. Assume that gas prices will rise by the rate of inflation (that you calculated in part a. Further assume that all gas expenditures are incurred at the end of the year. If the nominal interest rate is 9% per year, which car should you purchase? Show all calculations and explain carefully.

I think the interest rate is 116.67%

and i thought the answer for the total for model K waws $102,679.37 and for Model M was $79,977.67 but I am unsure if i did the math correctly.