"It is only the precise analysis of this complex of relations into the classical offer and acceptance, with identifiable consideration, that seems to present difficulty, but this same difficulty exists in many situations of daily life, e . g . sales at action; supermarket purchases; boarding an omnibus; purchasing a train ticket; tenders for the supply of goods; offers of reward; acceptance by post; warranties of authority by agents; manufacturers; guarantees; gratuitous bailments; bankers'commercial credits.