A furniture company has two plants that produce the lumber used in manufacturing tables and chairs. In 1 day of operation, plant A can produce the lumber required to manufacture 30 tables and 40 chairs, and plant B can produce the lumber to manufacture 25 tables and 50 chairs. The company needs enough lumber to manufacture at least 300 tables and 500 chairs. If it costs $1,000 to operate plant A for 1 day, and $800 to manufacture plant B for one day, how many days should each plant be operated to produce the sufficient amount of lumber at minimum cost