(a) A retail installment contract must be contained in a single document. The document must contain the entire agreement of the parties including promissory notes and other evidences of indebtedness between the parties relating to the transaction, except as provided in AS 45.10.040, 45.10.050, and 45.10.100.
(b) If the buyer's obligation to pay the time balance is represented by a promissory note secured by a chattel mortgage, a provision of the mortgage by which the buyer undertakes to do something besides pay a sum certain in money is considered to be contained in a separate document for the purpose of determining the negotiability of the note unless the provision is expressly incorporated in the note by reference to the provision of the mortgage.
(c) The contract must be dated, signed by the retail buyer, and completed as to all essential provisions, except as otherwise provided in AS 45.10.050 and 45.10.060.