Q. United Aluminum Industry of Cincinnati produces three grades ( high, medium, also low) of aluminum at two mills. Each mill has a different production capacity ( in tons per day) for each grade, as follows:
Mill
Aluminium
Grade 1 2
High 6 2
Medium 2 2
Low 4 10

The industry has contracted with a manufacturing organization to supply at least 12 tons of high- grade aluminium, 8 tons of medium- grade aluminium, also 5 tons of low- grade aluminium. It costs United $ 6,000 per day to operate mill 1 also $ 7,000 per day to operate mill 2. The industry wants to know the number of days to operate each mill in order to meet the contract at the minimum cost.