Attorneys Arianna and Alexander share an office that has a sign reading: "A & A, a law firm." Their billing invoices have both their names on them, and they deposit their earnings and cover the rent from the same account. They do not share profits or have any agreement to be partners. Dexter, a client of Arianna's for the past two years, sues both Arianna and Alexander, alleging that Arianna committed malpractice. If Dexter wins in court and is awarded $50,000 in damages, who is liable to him?