Philips, Inc. uses the periodic inventory system. Listed below are the transactions Philips, Inc. had for the month, March 2018.

Date	Transaction	# of units	Cost per unit
Mar. 1	Beginning balance	60	$20
Mar. 3	Purchase	25	$22
Mar. 9	Sale	30
Mar. 16	Purchase	35	$24
Mar. 18	Sale	50

4. Using FIFO, calculate the Cost of Goods Sold.

$ 950

$1,790

$ 800

$1,640

Answer: D

60*$20+20*$22=$1640

Where did the 20 come from?

please explain?