Metals Inc. needs 20 tons of iron, 15 tons of copper, and 8 tons of zinc to fill as particular order. They have two type of are available. Type A, which contains 15% iron, 5% coper, and 2% zinc costs $30 per ton. Type B which contains
10% iron, 10% copper, and 8% zinc costs $40 per ton. How much of each type should they use to minimize the cost?
What is the minimum cost?