dr. durango uses job order costing in her dental practice. some services, like root canals, involve multiple visits, often over more than a month's time. at the end of may, dr. durango had three patients with partially completed procedures. patient a had incurred direct material costs of $250 and direct labor costs of $300. patient b had direct material costs of $150 and direct labor costs of $150. patient c had direct material costs of $300 and direct labor costs of $300. dr. durango uses a direct labor rate of $100 per hour and applies overhead at the rate of $75 per direct labor hour. what was the balance in the work-in-process inventory account as of may 31?