HELLO ? CAN SOMEONE EXPLAIN the method sand how we did calculation

EXERCISE The following information was available from the inventory records of Rich Company for January: Units Unit Cost Total Cost Balance at January 1 3,000 $9,77 $29,310 Purchases: January 6 2,000 10.30 20,600 January 26 2,700 10.71 28,917 Sales: January 7 (2,500) January 31 (4,000) Balance at January 31 1,200 Required: a) Assuming that Rich does not maintain perpetual inventory records, what should be the inventory at January 31, using the weighted-average inventory method, rounded to the nearest dollar? (12,284 = 1,200 * (29 310 + 20 600 + 28 917) / 7 700 a) Assuming that Rich maintains perpetual inventory records, what should be the inventory at January 31, using the moving-average inventory method, rounded to the nearest dollar? (12,432 = 1,200 * (28 917 + (29 310 + 20 600) / 2) /5 200