A hotel has 40 guest rooms. After a period of business practice, the hotel manager discovered such a rule. If the room price is 40 yuan per day, the occupancy rate is 55%; when each room is priced at 35 yuan, the occupancy rate is 65%. When each room is priced at 30 yuan, the occupancy rate is 75%; when each room is priced at 25 yuan, the occupancy rate is 85%; when each room is priced at 20 yuan, the occupancy rate is full every day. In order to maximize the daily income, the manager should choose how many yuan per room per day from the above five pricing.
一个旅社有40间客房，经过一段时间的经营实践，旅社经理发现了这样一个规律，如果客房定价每间每天40元时，住房率为55%；每间定价35元时，住房率为65%；每间定价30元时，住房率为75%；每间定价25元时，住房率为85%；当每间价20元时，则天天客满．要使每天收入达到最高，经理应从上五种定价中选取每天每间为多少元．
<result>35</result>