an oil company requires at least 9,000 barrels of high grade oil, 12000 barrels of medium grade oil, and 20,000 barrels of low grade oil. It owns two refineries, say A & B. A produces 100, 300, and 400 barrels of high, medium, and low grade oil respectively per day; and B produces 200, 100, and 300 barrels of high, medium, and low grade oil respectively per day. Use the simplex method to solve the following.

1) If each refinery costs $50,000 per day to operate, then how many days should each operate in order to meet the demand and minimize the total cost of operation?

2) If the cost of refinery A increases to $70,000 per day, then how many days should each operate to meet the demand and minimize total cost of operation