(1) With respect to a consumer credit sale made pursuant to a revolving charge account, other than sales of real estate pursuant to section one hundred two of this article, the parties may contract for the payment by the buyer of a sales finance charge not exceeding that permitted in this section.

(2) A sales finance charge may be made in each billing cycle which is a percentage of an amount not exceeding the greatest of:

(a) The average daily balance of the account, or

(b) The balance of the account at the beginning of the first day of the billing cycle, less all payments on and credits to such account during such billing cycle and excluding all charges to such account during such billing cycle, or

(c) The median amount within a specified range within which the average daily balance of the account or the balance of the account at the beginning of the first day of the billing cycle, less all payments on and credits to such account during such billing cycle and excluding all charges to such account during such billing cycle, is included. A charge may be made pursuant to this paragraph only if the seller, subject to classifications and differentiations he may reasonably establish, makes the same charge on all balances within the specified range and if the percentage when applied to the median amount within the range does not produce a charge exceeding the charge resulting from applying that percentage to the lowest amount within the range by more than eight percent of the charge on the median amount.

(3) If the billing cycle is monthly, the sales finance charge may not exceed one and one-half percent on the first $750 of unpaid balance and one percent on the unpaid balance in excess of $750. If the billing cycle is not monthly, the maximum charge is that percentage which bears the same relation to the applicable monthly percentage as the number of days in the billing cycle bears to thirty. A billing cycle is monthly if the billing statement dates are on the same day each month or do not vary by more than four days therefrom.

(4) Notwithstanding subsection (3), if there is an unpaid balance on the date as of which the sales finance charge is applied, the seller may contract for and receive a charge not exceeding 50¢ if the billing cycle is monthly or longer, or the pro rata part of 50¢ which bears the same relation to 50¢ as the number of days in the billing cycle bears to thirty if the billing cycle is shorter than monthly.

(5) As an alternative to the loan finance charge allowed by section one hundred three, subsection (3) of this article, from the effective date of this subsection until and including July 1, 1982, with respect to a consumer credit sale made pursuant to a revolving charge account, other than sales of real estate pursuant to section one hundred two of this article, if the billing cycle is monthly, the sales finance charge may not exceed one and one-half percent on the unpaid principal balance. If the billing cycle is not monthly, the maximum charge is that percentage which bears the same relation to the applicable monthly percentage as the number of days in the billing cycle bears to thirty. A billing cycle is monthly if the billing statement dates are on the same day each month or do not vary by more than four days therefrom.