A steel mill produces two types of steel alloy: Boral and Chromal. Production of each alloy requires three processes: Box anneal, Cold Roll, and Strand anneal. Production capacities are: Box anneal: 4,000 hours/month Cold Roll: 500 hours/month Strand anneal: 1,000 hours/month. The maximum demand for boral is 10,500 tons/month and for chromal 6,000 tons/month. The contributions/ton are Boral: $25, and Chromal: $35. What combination of boral and chromal maximizes total monthly contribution?