88. Xiaoming and his sister Xiaomei go to two different schools, which are located to the east and west of their home, respectively. Xiaoming leaves home 6 minutes before his sister Xiaomei starts for her school. Two minutes after Xiaomei leaves, their father, who is at home, realizes that both Xiaoming and Xiaomei have forgotten their homework. So, he sets out on a bike to catch up with Xiaoming and Xiaomei to deliver their homework. It is known that the father's speed is three times that of Xiaoming and twice that of Xiaomei. Throughout the process of delivering the homework, Xiaomei and Xiaoming continue moving forward and do not reach their schools. How many minutes at least will the father need from the time he sets out until he returns home? $\qquad$
Reference answer: 16