a company sells a climbing kit and uses the periodic inventory system to account for its merchandise. the beginning balance of the inventory and its transactions during january were as follows: date units $/unit 1-jan beginning balance 18 13 12-jan purchase 30 14 19-jan sold 24 30 20-jan purchase 24 17 27-jan sold 27 30 if the ending inventory is reported at $357, what inventory method was used?