The CFO of a consulting engineering firm is deciding between purchasing Ford Explorers and Toyota 4Runners for company principals. The purchase price for the Ford Explorer will be $31,000. Annual maintenance costs for the Explorer are expected to be $600 per year more than that of the 4Runner. The purchase price for Toyota 4Runners is 35,000 The trade-in values after 3 years are estimated to be 50% of the first cost for the Explorer and 60% for the 4Runner. (a) What is the incremental ROR between the two vehicles?

a) The incremental ROR between the two vehicles is _____%.