The BMW salesman glanced at Della Whitfield’s faded farm dress, smirked in front of the entire showroom, and said, “You might want to try the used-car lot. That’s probably more your price range.”

He thought he was embarrassing a woman who couldn’t afford to be there.

What he didn’t know was that the plain envelope inside her canvas bag could cost his dealership the most valuable contract it had chased all year.