Brill saved the life of Ace's wife, Mary, who thereafter changed her will to leave Brill $1,000. However, upon Mary's death she had no property except an undivided interest in real estate held in tenancy by the entirety of Ace. The property had been purchased by Ace from an inheritance. After Mary died, Ace signed and delivered to Brill the following instrument: "In consideration of Brill's saving my wife's life and his agreement to bring no claims against my estate based on her will, I hereby promise to pay Brill $1,000." Upon Ace's death, Brill filed a claim for $1,000. Ace's executor contested the claim on the ground that the instrument was not supported by sufficient consideration."With respect to the recital that Brill had agreed not to file a claim against Ace's estate, what additional fact would most strengthen Brill's claim?
Brill's agreement was made in a writing he signed. Brill reasonably believed he had a valid claim when the instrument was signed. Mary had contributed to accumulation of the real property. Brill paid Ace $1 when he received the instrument.