A motor vehicle dealer may contract for and receive a documentary service charge for a retail or wholesale sale or lease of a motor vehicle. A documentary service charge shall be specified in writing without itemization of the individual services provided. A documentary service charge shall be not more than the lesser of the following:

1. (A) The amount allowed in a retail installment sale;
2. (B) Ten per cent of the amount the buyer or lessee is required to pay pursuant to the contract, excluding tax, title, and registration fees, and any negative equity adjustment.