There was no question of mistake on the part of either party before the moment when contract A came into existence. The tender, despite its being the product of a mistaken calculation, could be subject to the terms and conditions of contract A so as to invoke forfeiture of the deposit. There was no error in the sense that the contractor did not intend to submit the tender in its form and substance. Then, too, there was no principle in law under which the tender was rendered incapable of acceptance by the appellant. No mistake existed which impeded the coming into being of contract A. The effect of a mistake upon the formation, enforceability or interpretation of a subsequent construction contract need not be considered in this case.