A company uses weighted-average method of inventory valuation under periodic inventory system.The company began the year with a zero inventory balance.They had the following transactions during the year.

1.Purchased 65 units at 5 dollars per unit

2.Purchased 100 units at 5 dollars per unit

3.Sold 80 units at a price of 12.00 dollars per unit

4.Purchased 55 units at 6 dollars per unit

5.Sold 80 units at a price of 12,75 dollars per unit

At the end of the year,they counted the inventory and found 60 units remaining.Calculate the Cost of goods sold for the year.(Round your intermediate calculations to two decimal places)

a)420 dollars

b)577 dollars

c)840 dollars

d)315 dollars