Given the following data, calculate the cost of goods sold for the period using the weighted-average method for a periodic inventory system, rounding to the nearest dollar. (Do not round in the process of your calculations, only round your final answer.) 1/1 Beginning inventory 40 units at $12 per unit 3/5 Purchases 4/15 Sale 5/30 Purchases 11/15Sale 20 units at $14 per unit 30 units at $30 per unit 40 units at $11 per unit 50 units at $32 per unit 20 units Ending 12/31. inventory a) $960 b) $980 c) $966 d) $2,500