The opening time of the exhibition hall is 9:00 in the morning, and the closing time is 4:00 in the afternoon. How many hours is the opening time of this exhibition hall every day?
展览馆每天开馆时间为早晨9：00，闭馆时间为下午4：00，这个展览馆每天的开放时间是多少个小时．
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