can you please explain how reconciliation section works here? thanks.

PROBLEM 1 GIVEN 1.800 9,500 (A) BEGINNING RM COST RM PURCHASED ENDING RM BEGINNING WIP 2.150 (A) (A) OIH 3,500 12.800 4,350 4,200 7.500 6,100 ENDING WIP BEGINNING FG ENDING FG REQUIRED: PREPARE RM, WIP AND FG ANALYSIS RM: BEG RM ADD RM PURCH RM AVAIL LESS ENDING RM RM USED IN PRODUCTION 1,800 9.500 11,300 -2,150 9.150 WIP: BEG WIP ADD RM USED IN PRODUCTION ADD DL USED IN PRODUCTION ADD OH USED IN PRODUCTION TOTAL COST OF WIP LESS ENDING WIP COGM 3,500 9,150 12,800 4,350 29,800 4,200 25,600 FG: BEG FG ADD COGM GAFS LESS ENDING FG COGS 7,500 25,600 33, 100 -6.100 27,000 RECONCILIATION TOTAL RM PURCHASES, DIRECT LABOR & MFG OVERHEAD (SUM A) 26,650 RM INV CHANGE (INCREASEVDECREASE WIP INV CHANGE (INCREASE DECREASE FG INV CHANGE (INCREASE YDECREASE -350 -700 1,400 COGS 27,000