A company sells garden hoses and uses the perpetual inventory system to account for its merchandise. The beginning balance of the inventory and its transactions during September were as follows:September 1: Beginning balance of 18 units at $13 each September 12: Purchased 30 units at $14 each September 19: Sold 24 units at $30 selling price each September 20: Purchased 24 units at $17 each September 27: Sold 27 units at $30 selling price eachIf the ending inventory is reported at $276, what inventory method was used?（ ）