Xiao Li, Xiao Ming and Xiao Hong. Xiao Ming, Xiao Hong and Xiao Li are going to borrow the book Little Doudou by the Window from the library (only 1 volume). Xiao Ming said he could finish it in a week, Xiao Hong said he could finish it in half a month and Xiao Li said he could finish it in five days. Xiao Li 5 days, Xiao Ming 7 days, Xiao Hong 15 days. If you want to have the least total waiting time, you must arrange it from less to more, so the order of borrowing is Xiao Li, Xiao Ming and Xiao Hong, so the total waiting time of three people is the least.