a paper mill produce two grades of paper viz., x and y. because of raw material restriction,it cannot produce more than 400 tons of grade x and 300 tons of grade y paper in a week.there are 160 production hours in a week.it require 0.20 and 0.40 hours to produce a tons of grade x and y paper.the mill earns a profit of rs. 200 and 500 per ton of grades x and y respectively.formulate this a an linear programming problem