Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases. During December. Monson sells 15 units for $20 each on December 15. Purchases on December 7 Purchases on December 14 Purchases on December 21 15 Assume the periodic inventory system is used. Determine the costs assigned to ending inventory when costs are assigned based on the weighted average method. (Amounts to be deducted should be indicated with a minus sign. Round cost per units to 2 decimals.)