SECTION 1. Notwithstanding any General or special law, or any rule or regulation, to the contrary, every contract for the sale of any item in the Commonwealth, which has been advertised or promoted in any way to permit a purchaser to defer any interest relating to the sale such item until either the time specified in said contract has passed or the principle price ,or any portion thereof, has been paid off, shall state conspicuously on said contract, in a similar style and size of print, the total amount of interest in dollars due and is required to be paid by said purchaser at the time said deferment and what the difference would to be in total dollars to be paid on such a sale if such a purchaser had paid for said item in full at the time of the sale  and had not deferred such payment. Any such contract shall in likewise manner, and in keeping with this section, state if the amount of interest is to be started and calculated from the time of the sale of the item or if from the date of the deferment.