[Wrong Deck] Gina Hires Jackson Over the Telephone to Paint

[Wrong Deck] Gina hires Jackson over the telephone to paint her back deck. She tells him her address and agrees to pay him $200 for the job, and he accepts. They enter into the agreement on Tuesday, and he is to paint the deck on Saturday. Jackson had a little difficulty finding her house because he spilled coffee on the note where he wrote her address. When Jackson arrives, neither Gina nor her neighbor is at home. He mistakenly paints the neighbor's deck. Gina calls him the next day and asks him why he did not paint her deck. He informs her that he did paint the deck. When it is discovered that he mistakenly painted the neighbor's deck, Gina tells him not to worry because the neighbor will be required to pay him. Jackson says that if the neighbor does not pay, then he expects all of the payment from Gina, because the contract is executed.
-Which statement is true regarding Jackson's assertion that Gina must pay him if the neighbor fails to do so?

A) He is correct because an express contract existed, and he made an honest mistake for which Gina must accept the risk.
B) He is correct because an implied contract existed, and he made an honest mistake for which Gina must accept the risk.
C) He is correct because an implied-in-law contract existed.
D) He is correct because a valid contract existed; and, after his performance, it is considered executed.
E) He is incorrect unless he can somehow establish that Gina gave him poor directions or was otherwise at fault in informing him which deck to paint, and the contract remains executory.