Due to the weather, the spring outing scheduled to be canceled tomorrow will take 1 minute to make a phone call. If the best way to make a phone call is the best way, how many minutes will it take for Mr. Wang to let the whole class of 30 people know the news.
由于天气原因，原定明天的春游取消，打一个电话要1分钟，如果用打电话的最佳方式，王老师至少需多少分钟才能使全班30人都知道这一消息．
<result>5</result>