Ella hired a contractor named Robert to carefully drill a well on her property. The two parties entered into a contract that said that Ella was to pay Robert $9,000 upon completing the work. Robert asked Ella if she would pay an additional $3,000 to complete his work during the well project. Robert explained that he had underestimated the amount of work to do for this well and could not complete the work without an additional payment. Ella agreed to pay him the additional money after Robert said he would be careful to not damage or ruin Ella's landscaping during the well drilling. Ella signed an amendment to the original contact that promised to pay the additional $3,000. Ella's signature on the amendment contract was duly notarized. Robert was careful while drilling, and no damages happened to Ella's landscaping.

After this project, what amount of money does Ella LEGALLY owe Robert? Talk about the legal issues. Do not talk about the parol evidence rule, or the liquidated or unliquidated debt.