Answer:
A first-price sealed bid auction (blind auction) is a normal auction, where all the bidders submit their bids (sealed) simultaneously and no bidder knows the bid of any other participants.
The highest bidder pays the price they had submitted.
Suppose there are two bidders '1' and '2', whose valuations are 'V1 = 10' and 'V2 = 10'.
Also, assume that the bidder '2' submits a bid 'b2 = 10'.
If a bidder does not know the bid submitted by other participant, then he/she will submit his/her bid 'b1 = 10' as well because any number less than '10' will reduce his/her chances of winning the auction.
Hence, the bid submitted by bidder '1' is equal to b1 = 10
If both the bidders submit b1 = b2 = 10', then their pay-offs (profits) will be zero as this is their maximum valuation. Both will have zero pay-offs.
Hence, the pay-off of bidder “1” is zero