Please provide a detailed clear solution, will upvote

Design a fair bidding protocol based on the cryptographic tools you have studied in the subject. The protocol should consist of a seller/organiser and multiple buyers/bidders. There are two phases in the protocol: bid collecting phase, and result announcing phase. You can assume there exists a trusted public bulletin board (e.g., a forum) for all the bidders and the organizer to publish their messages in both phases. The published messages are visible by everyone. Describe clearly each step of your protocol. Provide justifications for the fairness achieved by your proposed protocol