[Cheap Principal] Paolo, Who Is Very Knowledgeable Regarding Computers, Agrees

[Cheap Principal] Paolo, who is very knowledgeable regarding computers, agrees to purchase computers for Joe's business. Paolo is retained for that purpose only, he is paid a set rate for the job, and Joe exercised no control over the manner in which Paolo did his work. Paolo purchased computers from AAA Computers without any mention of Joe. The computers worked well and were not defective in any way. Unfortunately, Joe did not pay AAA Computers on a timely basis. Paolo, therefore, paid AAA Computers out of his own pocket because he wanted to be able to do business with AAA Computers in the future and also because his name was on the invoice. Paolo asked Joe for reimbursement, but Joe refused. Joe claimed that if Paolo had only waited, AAA Computers might have agreed to take less.
-Did Paolo have any legal liability to AAA Computers?

A) Yes, because he made the purchase from AAA Computers without mention of Joe.
B) Yes, but only because office equipment is involved.
C) No, because his status was as an agent regardless of whether AAA Computers was aware of that fact.
D) Yes, but only if Joe refused to pay.
E) Yes, but only if Joe were declared judicially insolvent.