math question help

The Pine Valley Credit Union is trying to schedule bank tellers. The credit union is open 8am-6pm and needs the following number of tellers each hour. Full-time tellers can work 8am-5pm (with a 12-1 lunch hour) or 9am-6pm. (with a 1pm-2pm lunch hour). Part-time tellers work 10am-2pm. Full-time tellers receive $300 per day and part-time tellers $60 per day. At most four part-time tellers can be hired. How can the credit union minimize their daily salary cost?