A contractor with a contract to deepen a well in a drought-stricken area mistakenly entered onto the wrong property and proceeded to deepen the well there. The owner of the property saw the contractor at work but said nothing. When the contractor completed the job, the property owner refused to pay his bill, and the contractor filed suit. In her answer, the property owner stated that she thought the contractor was employed by the county and that the government was paying for the work because of the drought. She knew, however, that two of her neighbors had recently paid private contractors to deepen their wells. Which of the following arguments offers the contractor his best chance for winning his lawsuit?

Group of answer choices

Promissory estoppel.

Mutual mistake.

Unilateral mistake.

Implied-in-fact contract.