Sec. 604. Limitation on Default Charges in Consumer Related Sales — (1) The agreement with respect to a consumer related sale may provide for only the following charges as a result of the buyer's default:
(a) reasonable attorney's fees and reasonable expenses incurred in realizing on a security interest;
(b) deferral charges not in excess of twenty-five percent (25%) per year of the amount deferred for the period of deferral; and
(c) other charges that could have been made had the sale been a consumer credit sale.
(2) A provision in violation of this section is unenforceable.