Answer:
d. maria would not have to pay anything.
Explanation:
In this scenario Maria did not form a contract with the man to cut her lawn and had not even met him before. So there is no contract formed voluntarily, neither is it an implied contract.
Maria was enriched in this process because she will benefit from the cutting of the lawn. She was however not unjustly enriched because the man was not unduly influenced to carry out the task.
Maria can however pay the man after the fact at her discretion.