Anyone help me figure out how the factory's profit is calculated...

500 (as if the total income cash and revenue amount equal, not taking into account taxes) - 120 (as if your raw materials have been fully processed, finished goods all sales carryover costs) - 5-80-5 = 290

profit of 2.9 million yuan

You give incomplete information, the total investment of 13 million, the formation of a long-term asset, has nothing to do with profit, unless there is investment income ; receivables and payables, which are assets and liabilities not related to profit