Ed's car broke down on a dark, rainy night. Along came Bev in her service station's four-wheel drive truck with tools and supplies in the back. Ed didn't have any credit cards and only $3.25 cash, so Bev told him to write a check or an IOU. Neither Bev nor Ed had any paper, so Ed wrote on the cover of Bev's magazine: "If my car is fixed right by Bev Brady, I will pay her $150. (Signed) Ed Wasner." Bev indorses the note and takes it to a commercial bank for negotiation. The bank refuses, saying it is non-negotiable because it: a. is conditional on satisfactory repair of the car. b. is written on a lunchbox. c. mentions the existence of a contract to repair the car. d. None of these are correct.