Answer:
Date    Particulars                                       Debit            Credit
            Deferred Service Revenue A/c     $4,000
                      To Revenue A/c                                           $4,000
             (Being Revenue recognized)
           Advertisement Expense  A/c           $2,600
                   To Prepaid Advertisement A/c                      $2,
600
           (Being expense recognized)
            Employees Salaries A/c                  $16,000
                   To Outstanding Employees Salaries A/c      $16,000
            (Being expense & liability recorded)
            
              Interest expense A/c                      $1,600
                            To Interest Liability A/c                            $1,600
              (Being Interest expense & Liability for the 
                month September to December recorded)
Assumptions & Working notes:-
i) Since service is performed in the same financial year revenue is transferred from deferred revenue account to revenue account.
ii) Since 20 advertisements shown in the month of December only so expense related to those 20 is recognized in the month of December and remaining in the month of January.
$5,200/40*20 = $2,600
iii) Since salaries are paid in month of January but this is the expense for the month of December we recorded above entry.
iv) Interest Expense for months September to December is recorded and corresponding liability is created.
($60,000 * 8%) / 12 * 4 = $ 1,600