Answer with explanation

Roger was late for class. He rushed up to the front of the college, parked his bicycle beside the front door, and ran inside to his class. Leonard, who was standing just inside the door, saw Madeleine stop to admire the bike, and as she came through the door, Leonard asked her if she would be interested in buying it for $90. She offered to pay $70, and Leonard accepted. She wrote a cheque, and Leonard went to the bank to cash the cheque. Madeleine got on the bike and rode it home. When Leonard got back from the bank, he went to the room where Roger's class was just over. He offered to buy Roger's bike from him for $25. Roger said he would not sell it for less than $50. They discussed it and soon came to an agreement at $40. Leonard handed over the $40 in cash. Discuss the legality of the events in this case. If Leonard had not agreed to buy the bike, and Roger had seen Madeleine riding his bike around the campus, what rights would Roger have?