Janine was hospitalized with severe abdominal pain and placed in an intensive care unit. Her doctor told hospital personnel to order around-the-clock nursing care for Janine. At the hospital's request, a nursing services firm, Nursing Services Unlimited, provided two weeks of in-hospital care and, after Janine was sent home, two additional weeks of at-home care. During the at-home period of care, Janine was fully aware that she was receiving the benefit of the nursing services. Nursing Services later billed Janine $4,000 for the nursing care, but Janine refused to pay on the ground that she had never contracted for the services, either orally or in writing. In view of the fact that no express contract was ever formed, can Nursing Services recover the $4,000 from Janine? If so, under what legal theory? Discuss.