Darlington wants to build recreational centre, places ad in local paper, requests contractors submit tenders - must be received by June 15, 4pm, irrevocable after received R submits tender, but after deadline realizes he made miscalculation, bid grossly understated; he contacts city, asks his tender be removed Though city has yet to select winning tender, it rejects his request, will pick his if lowest bid Question: is R able to revoke his bid?