Bids may be made by the principal or his agent, either personally or by mail. Bids will be considered only if received at the place and prior to the hour fixed in the notice. No particular form is specified for bids. However, a bid must be in writing, clearly identify the bidder, be signed by the bidder or his designated agent, state the amount of the bid, and refer to the notice. Bids conditioned in ways not provided for by the notice will not be considered. Bids must be accompanied by certified checks, post office money orders, bank drafts, or cashier's checks made payable to the United States of America for 2 percent of the amount of the fair market value or $2,500, whichever is greater, in the case of a freehold interest or for the amount of the first year's rent in the case of a leasehold interest. This payment will be refunded to unsuccessful bidders. A separate nonrefundable payment of $100 to cover costs of publication and of processing of bids will also be included with the bid. The bid and payments must be enclosed in a sealed envelope upon which the prospective bidder shall write: (a) Bid on interest in land of the National Park System, and (b) the scheduled date the bids are to be opened. In the event two or more valid bids are received in the same amount, the determination of which is the highest will be by drawing. Bids will be opened at the time and place specified in the notice. Bidders, their agents or representatives, and any other persons may attend the bid opening. No bid in an amount less than the fair market value, as herein defined, shall be considered.