The demand for a product of an automile company changes from month to month. The probability distribution is given based on the past two years of data which shows the company's monthly demand.

Unit demand 300, 400, 500, 600. Probability 0.20, 0.30, 0.35, 0.15.

If the company bases monthly orders on the expected value of the monthly demand, what should the automobile company monthly order quantity be for this product?