Captain Tuan, Hoban, Orrin, Kentari and Anshu decided to go sailing to other worlds for the vacation. During the time on the ocean, they had a bad storm and broke their ship into pieces. Fortunally, all of them survive were able to get to an island nearby. A small boat was with them also.
After a few days, Hoban located a nearby bigger island where there are a lot of fruits to eat and wood to build a ship to go back home. The problem is only maximum two of them can fit in the boat so they have to travel back and forth to get all of them to the other island.
If Hoban sails alone, it would take him 1 day to get to the next island. For Captain Tuan, it's 2 days. For Kentari, it's 5 days. For Orrin, it's 10 days. And for Anshu, it's 10 days. If two of them sail together, the time to travel is the time of slower one (the slower one drag down the speed).
Question: What is the shortest time to take all of them to the other island?
Prize: Finding Cyodrakes Gaze
Deadline: A week after the posted time.
You are allowed to answer up to 3 times. Discussion can be posted in the discussion thread. Please justify your answer (i.e. provide your solution).