Answer:
Harold should be considered an undisclosed principal.
Step-by-step explanation:
Basically Alice hid Harold's identity from Sarah, and she negotiated the purchase of the lot pretending to be the principal herself. Sarah was convinced that Alice was purchasing the lot for herself and not on behalf of someone else.
In this case, Alice is in trouble because she is personally bound on the contract with Sarah, and she doesn't seem to want the lot.