You're working on a MongoDB database for a video game where players can sell their items, such as planks, to other players.

The Mongo Shell code to trade planks between players is the following:

// The seller and buyer variables were set to the ids of the seller and the buyer, respectively
// They both exist in the database
sellerPlayer = db.Players.findOne({ _id: seller });
buyerPlayer = db.Players.findOne({ _id: buyer });
if (sellerPlayer.planks >= 100 && >= 350) {
    db.Players.update({ _id: seller }, { $inc: { gold: 350, planks: -100 }});
    db.Players.update({ _id: buyer }, { $inc: { planks: 100, gold: -350 }});

What can be said about the code above in cases with no disconnections from the server?

(Select all acceptable answers.)

It's possible for a seller to end up with negative planks if multiple purchases are done at the same time.
The code queries and updates the Players collection.
The gold of the seller might be increased multiple times with just one reduction in the plank count.
The updates could be rewritten as a single update taking the parameter { _id: seller, _id: buyer } as the query.
The updates need { multi: true } to work correctly.
findAndModify calls can be used instead of the update operations and still get the same results.

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