Use the following steps:-
1. Send two family members who have speed 1 and 3.
2. Send back the person whose speed is 3.
3. Send two family members who have speed 8 and 12.
4. Send back the person whose speed is 1.
5. Send two family members who have speed 6 and 1.
6. Send back the person whose speed is 1.
7. Send last two family members.
Complete.