Presented Below Are the Year-End Balances at December 31 of Laura's

Presented below are the year-end balances at December 31 of Laura's Laundry Service. (All accounts have normal balances.)
$$\begin{array} { | l | r | } \hline \text { Accounts receivable } & \$ 12,000 \\\hline \text { Accounts payable } & 25,000 \\\hline \text { Accumulated depreciation - Catering equipment } & 30,000 \\\hline \text { Advertising expense } & 4,000 \\\hline \text { Cash } & 42,000 \\\hline \text { Depreciation expense - Catering equipment } & 12,000 \\\hline \text { Insurance expense } & 3,000 \\\hline \text { Catering equipment } & 125,000 \\\hline \text { Catering service revenue } & 200,000 \\\hline \text { Notes payable } & 65,000 \\\hline \text { Common stock } & 3,000 \\\hline \text { Retained earnings } & 14,000 \\\hline \text { Dividends } & 18,000 \\\hline \text { Prepaid insurance } & 1,500 \\\hline \text { Salaries payable } & 4,000 \\\hline \text { Salary expense } & 97,000 \\\hline \text { Supplies } & 1,500 \\\hline \text { Supplies expense } & 9,000 \\\hline \text { Repair expense } & 7,000 \\\hline \text { Unearned catering service revenues } & 500 \\\hline \text { Utilities expense } & 9,500 \\\hline\end{array}$$
a. Prepare the necessary closing entries at December 31.
b. Prepare a post-closing trial balance at December 31.