Chork's Puzzle 44

Difficulty Rating: 1

It was raining really heavily and 4 children, Armin, Bob, Chork and Don were stuck in school. They all wanted to get to the nearby MRT station but the route there was completely unsheltered and they all didn't want to get wet. Luckily, they had an umbrella. However, the umbrella could only shelter 2 people at any one time.

Armin takes 3 minutes to cover the distance from school to the MRT station (and vice versa). Bob takes 4 minutes. Chork takes 6 minutes and Don, who is rather slow, takes 10 minutes.

Now, their task is to get to the MRT station in the shortest time possible. However, note that when 2 people are sharing an umbrella, the faster person must accomodate the slower one and walk at his speed. Also, someone would have to bring the umbrella from the MRT station back to school so that the remaining children can continue using the umbrella.

What is the shortest time needed to get all 4 children to the MRT station, sheltered with an umbrella?
If you know the answer, post it in the comments section of this post.