Select all that apply Why is it expressly more difficult to determine optimal bidding strategies with correlated values than with independent private values? Multiple select question. Bidders know their own valuations, but not those of others. Bidders don't know their own valuations. Bidders learn the valuation of others through the auction process. Bidders know the valuations of others. Bidders don't know the valuations of others at the outset of the auction