A paper mill produces two grades of paper viz., X and Y because of raw material restrictions, it cannot produce more than 400 tons of grade X paper and 300 tons ot grade Y paper in a week. there are 160 prodection hours in a week. it requires 0.20 and 0.04 hours to produce a ton of grade X and Y papers. the mill earns a profit of Rs 200 and Rs 500 per ton of grade X and Y paper respectively.formulate this as a linea programming problem.