The CFO of a consulting engineering firm is deciding between purchasing Ford Explorers and Toyota $4$Runners for company principals. The purchase price for the Ford Explorer will be $$29,250.$ Annual maintenance costs for the Explorer are expected to be $$650$ per year more than that of the $4$Runner. The purchase price for Toyota $4$Runners is $36,000$ The trade$-$in values after $3$ years are estimated to be $50\%$ of the first cost for the Explorer and $60\%$ for the $4$ Runner. $($a$)$ What is the incremental ROR between the two vehicles? $($b$)$ Provided the firm's MARR is $30\%$ per year, which vehicle should it buy?

a$)$ The incremental ROR between the two vehicles is

$\%.$

b$)$ The firm should buy as the incremental ROR is the MARR.