For conducting Third Semester Practical Examination, the Chemistry department of a university affiliated college requires 10, 12 and 7 units of three chemicals X, Y and Z respectively. The chemicals are available in two boxes-box A and box B. Box A contains 3, 2 and 1 unit of X, Y and Z respectively and costs ₹ 300. Box B contains 1, 2 and 2 units of X, Y and Z respectively and costs ₹ 200. Find how many boxes of each type should be purchased by the department so that the total cost is minimal by formulating the problem in linear programming problem and solve it through graphical method?