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Question 6

Hint 1:

The provided mlist-find-best procedure is like list-find-best but works on mutable lists. To find the highest bid, you could use mlist-find-best on the entries of the bid table, using the bid amount for selecting the best bid.

Hint 2:

Don't forget to deal with the case when there are no bids on the item. You might want to start by checking the list of entries is non-empty.