Mohan purchased goods for Rs. 15,00,000 and sold 4/5th of the goods amounting Rs. 18,00,000 and paid expenses amounting Rs. 2,70,000 during the year, 2005. He paid Rs. 5000 for an electricity bill of Dec. 2004 and advance salaries amounting Rs. 15,000 was paid for the month of Jan. 2006. He counted net profit as Rs. 3,50,000.
The profit calculated by him is correct according to ___________.