I cant figure out how to calculate A. B. or C.

The December 31, Year 4, balance sheet for Gibson Corporation is presented here. These are the only accounts on Gibson'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.)