Using the accounting equation

Question _________ At January 01, 20X9, Robert's business assets were valued at $ 36,000 and his liabilities amounted to $ 2400. At 31st Dec, 20X9, Robert's assets amounted to $ 57,000 and included his private car which he had brought into the business on 1st Nov when it was valued at $9000. His trade receivables at 31st December totaled $ 17,000. His drawings during the year were $ 27,000. Required __________ Calculate profit for the year ended 31st December 20X9. Accounting year - 01-01-20X9 to 31-12-20X9 Opening assets - $ 36,000 Opening liabilities - $ 2400 Opening capital = $ 36,000 - $ 2400 = $ 33,600 Closing capital = $ 57,000 - $ 17,000 = $ 40,000 Using accounting equation, Profit = closing capital - opening capital - additional capital + drawings Profit = $ 40,000 - $ 33,600 - $ 9,000 + $ 27,000 Profit = $ 24,400. CONFUSION In this answer, I am confused about calculation for closing capital. A) Should not we include receivables because receivables are current assets and closing capital = closing assets Less closing liabilities?? B) Should not we subtract $9000 worth of private car introduced in business from closing capital figure?? like $ 57,000 - $ 9,000 = $ 48,000 (closing capital) Thank you!