the direct labor rate for brent corporation is $9.00 per hour, and manufacturing overhead is applied to products using a predetermined overhead rate of $6.00 per direct labor-hour. during may, the company purchased $60,000 in raw materials (all direct materials) and worked 3,200 direct labor-hours. the raw materials inventory (all direct materials) decreased by $3,000 between the beginning and end of may. the work in process inventory on may 1 consisted of one job which had been charged with $4,000 in direct materials and on which 300 hours of direct labor time had been worked. there was no work in process inventory on may 31.