Answer all question cover topics of the Malaysian Legal System and Law of Contract

Sam decided to sell his year-old Sony A7C camera. He put up a post in Facebook stating that the camera is for sale for RM6000. Ali saw the post and responded to it stating that he wants to buy the camera but he wants to inspect it first. Sam did not respond.John, who is Sam's neighbour, went Sam's houseafter seeing the post and told him that he wants the camera and gave him a cheque for RM6000 for it. Sam refused to accept the cheque and John told Sam that he will sue Sam for breach of contract. Abu saw the post and contacted Sam stating that he is willing to pay the stated price provided Sam gave him a month's warranty against any defect. Sam told him that he needs two days to consider Abu's proposal. Gurmit, who knows Sam, immediately went to Sam's house after seeing the post and offered RM5800 cash for the camera which Sam accepted.

Advise Ali, John and Abu whether they can compel Sam to sell the camera to them instead.