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Order, Supreme Court, New York County (Barbara R. Kapnick, J.), entered October 8, 2003, which denied plaintiff's motion for summary judgment, and granted defendant's cross motion for summary judgment dismissing the complaint, unanimously affirmed, with costs.

The phrase in the policy to "do your best" is unambiguous, and has a clear and unmistakable meaning (see Goldman & Sons v Hanover Ins. Co., 80 NY2d 986 [1992]). The undisputed evidence establishes that plaintiff failed to purchase oil for the heating tank or to contract with an oil supplier for the premises during the 18 months from its acquisition of the premises until the water damage resulting from the frozen pipes. In addition, plaintiff's caretaker was not instructed on how to maintain the heat, and was never even told that the premises were heated with oil, how to check for oil in the tank, or where the oil tank was located. Under any reasonable interpretation, plaintiff failed to "do [its] best" to maintain heat in the building. Concur—Buckley, P.J., Tom, Sullivan and Williams, JJ.