The seven-person maintenance function at a hospital performs both preventive and corrective maintenance on hundreds of items each month. All the workers are scheduled for 40 hours per week and there are four weeks in a month. It is the goal of the maintenance department to achieve 90% utilization with a mix of two-thirds preventive maintenance and one-third corrective maintenance. How many hours each month are spent performing corrective maintenance if they achieve their 90% utilization and corrective /preventive mix targets?