A paper mill products two grade of paper viz., X & Y. Because of raw material restriction, it cannot produce more than 400 tons of grade X paper & 300 tons of grade Y paper in a week. There are 160 production hours in week. It requires 0.20 & 0.40 hours to produce a ton of grade X & Y papers. The mill earns profits of Rs.200 & Rs.500 per ton of Grade X & Y paper respectively. Formulate this as a Linear Programming Problem.