12. Xiao Ming's school schedule has changed. He arrives at school at 8:30 in the morning, has lunch at school at noon, and leaves school at 3:30 in the afternoon. What is Xiao Ming's day at school?
12、小明的学校作息时间改变了，早上8：30到校，中午学校就餐，下午3：30放学，小明一天在校时间是多少．
<result>7</result>