The following lots of a particular commodity were available for sale during the year: Beginning inventory First purchase Second purchase Third purchase 10 units at $61 25 units at $63 30 units at $64 15 units at $73 The firm uses the periodic system and there are 20 units of the commodity on hand at the end of the year. What is the amount of the inventory at the end of the year according to the average cost method? a. $1,300 b. $1,305 c. $1,415 d. $1,236