A company has two grades of inspectors, 1 and 2, who are to be assigned for a quality control inspection. It is required that at least 1800 pieces be inspected per 8-hour day. Grade 1 inspectors can check pieces at the rate of 25 per hour, with an accuracy of 98%. Grade 2 inspectors check at the rate of 15 pieces per hour, with an accuracy of 95%. The wage rate of grade 1 inspector is $4.00 per hour, while that of a grade 2 inspector is $3.00 per hour. Each time an error is made by an inspector, the cost to the company is $2.00. The company has available for the inspection job eight grade 1 inspectors, and ten grade 2 inspectors. The company wants to determine the optimal assignment of I inspectors, which will minimize the total cost of the inspection. Formulate the problem as integer programming problem and solve it using branch and bound method.