The following units of an inventory item were available for sale during the year: Beginning inventory 12 units at $51 First purchase 17 units at $53 Second purchase 28 units at $55 Third purchase 16 units at $56 The firm uses the periodic inventory system. During the year, 21 units of the item were sold. The value of ending inventory rounded to the nearest dollar using average cost is (Round average cost per unit to three decimal places.) a. $1,089 Ob. $2,813 Oc. $1,171 Od. $1,071