Answer:
$6
Step-by-step explanation:
bidder 1:
50% chance paying $5
50% chance paying $7
expected value = ($5 x 50%) + ($7 x 50%) = $6
bidder 2:
50% chance paying $3
50% chance paying $10
expected value = ($3 x 50%) + ($10 x 50%) = $6.50
According to Myerson's optimal reserve price theory, the reserve price does not depend on the number of bidders, instead it depends on the distribution of the buyers' valuation. In this case, both buyers' valuations are very similar, $6 and $6.50, so one of them should be the reserve price. Since this is an open bid and the reserve price will probably serve as reference point, the reserve price should be $6 so that both bidders can participate and hopefully the price will exceed $7 (the highest second bid).