Mark decided to purchase a new automobile. Being concerned about environmental issues, he isleaning toward the hybrid rather than the gasoline only model. Nevertheless, as a new business school graduate, he wants to determine if there is an economic justification for purchasing the hybrid, which costs $1,000 more than the regular model. He has determined that city/highway combined gas mileage of the hybrid and regular models are 30 and 24 miles per gallon respectively. Mark anticipates he will travel an average of 10,000 miles per year for the next several years.

The payback period of the incremental investment if gasoline costs $3 per gallon is: