Last Monday, I opened my car door and knocked a man off his bike. He was Ok thank goodness. His helmet was cracked so I said I would get him another one. I tried to ring him the next day to organise to do that but he did not answer. I left a message. Yesterday he text me asking for $230 to replace his helmet and mobile phone which were damaged in the car accident. I don't really have a problem with this but I think I should be buying it not handing over money. I have asked him for copies of his receipts for the replacement of these items. What am I legally liable for under traffic law?