During 1976 a series of arsons, one of which damaged the Humongous Store, occurred in the City of Swelter. In early 1977 Swelter's City Council adopted this resolution: The City will pay $10,000 for the arrest and conviction of anyone guilty of any of the 1976 arsons committed here. The foregoing was telecast by the city's sole television station once daily for one week. Subsequently, Humongous, by a written memorandum to Gimlet, a private detective, proposed to pay Gimlet $200 "for each day's work you actually perform in investigating our fire." Thereafter, in August 1977, the Swelter City Council by resolution repealed its reward offer and caused this resolution to be broadcast once daily for a week over two local radio stations, the local television station having meanwhile ceased operations. In September 1977, a Humongous employee voluntarily confessed to Gimlet to having committed all of the 1976 arsons. Humongous's president thereupon paid Gimlet at the proposed daily rate for his investigation and suggested that Gimlet also claim the city's reward, of which Gimlet had been previously unaware. Gimlet immediately made the claim. In December 1977, as a result of Gimlet's investigation, the Humongous employee was convicted of burning the store. The city, which has no immunity to suit, has since refused to pay Gimlet anything, although he swears that he never heard of the city's repealer before claiming its reward"Which of the following best characterizes the relationship between Humongous and Gimlet?
A unilateral offer of employment by Humongous which became irrevocable for a reasonable number of days after Gimlet commenced his investigation of the store's arson. An employment for compensation subject to a condition precedent that Gimlet succeed in his investigation. A series of daily bilateral contracts, Humongous exchanging an express promise to pay the daily rate for Gimlet's implied promise to pursue his investigation with reasonable diligence.  A series of daily unilateral contracts, Humongous exchanging an express promise to pay the daily rate for Gimlet's daily activity of investigating the store's arson