4) The following information is provided for Castle Company. All liabilities are due to be satisfied within one year unless stated otherwise. Retained earnings $ 52,000 Supplies Equipment Accounts receivable 37,000 72,000 9,000 Deferred revenue 6,000 Accounts payable 18,000 Common stock 25,000 Notes payable (due in 18 months) 35,000 Interest payable 7,000 Cash 22,000 What is the amount of current liabilities? a. $22,000 b. $28,000 c. $31,000 d. $46,000