4(2)For the purposes of calculating the benchmark price for a type of heating fuel or motor fuel over a 7 day period, the daily high and low prices attributed to a base product for any Saturday, Sunday or day that is a statutory holiday in the State of New York or, in the case of propane, in the Province of Ontario, shall be deemed to be the prices in effect for that base product on the last business day immediately preceding the Saturday, Sunday or statutory holiday, as the case may be.