Rob, a wealthy philanthropist, placed an advertisement in the ‘Herald’ newspaper offering to sponsor, at the rate of £1 per mile, anyone willing to walk to Manchester in aid of the Contract Lecturers’ Benevolent Fund, a charity. Elizabeth, who was already walking to Manchester in order to improve her fitness, heard about Rob’s advertisement and decided to claim the sponsorship money on arrival in Manchester. Richard read the advertisement and decided to set out for Manchester, having first sent an email to Rob informing him that he intended to claim the sponsorship money. When Rob received Richard’s email, he placed a second advertisement in the ‘Herald’ revoking his offer, which Yvonne, a friend of Richard told him about when he was half-way to Manchester. Meanwhile, Stewart, who had read Rob’s first advertisement, set out for Manchester having decided to claim the sponsorship money, but did not hear of Rob’s second advertisement. Elizabeth heard of Rob’s second advertisement before she reached Manchester and gave up her walk before reaching Manchester, but claimed to be entitled to £1 per mile for every mile she had covered. Richard completed the walk and claimed the sponsorship money, as did Stewart when he completed the walk. Advise Rob.