Please explain why the answer is 600,000 and how to calculate it with steps

Use the following data to determine the total dollar amount of assets to be classified as current assets. Koonce Office Supplies Balance Sheet December 31, 2017 Accounts payable Salaries and wages payable Mortgage payable Total liabilities $ 210.000 30,000 240,000 $480,000 Cash $ 195,000 Accounts receivable 150,000 Inventory 165,000 Prepaid insurance 90,000 Stock investments 255,000 Land 270,000 Buildings $315,000 Less: Accumulated depreciation_(60,000) 255,000 Trademarks 210,000 Total assets $1,590,000 Common stock Retained earnings Total stockholders' equity Total liabilities and stockholders' equity $360,000 750,000 $1,110,000 $1.590.000 a. $855,000 b. $600,000* c. $510,000 d. $435,000