The December $31,$ Year $4,$ balance sheet for Perez Corporation is presented here. These are the only accounts on Perez's balance sheet. Amounts indicated by question marks $(?)$ can be calculated using the following additional information:

Required

a$.$ Compute the balance in trade accounts payable as of December $31,$ Year $4.$

b$.$ Compute the balance in retained earnings as of December $31,$ Year $4.$

c$.$ Compute the balance in the inventory account as of December $31,$ Year $4.($Assume that the level of inventory did not change from last year.$)$