Xiao Ming walks 6 kilometers to his grandma's house at 7:40. His walking speed is 3 kilometers per hour, but he has to rest for 10 minutes every 40 minutes of walking. When will he arrive?
小明7：40步行去6千米的奶奶家，他步行速度是每小时3千米，但他每走40分钟就要休息10分钟，则他多少时到．
<result>10</result>