163526

It took a while to solve this puzzle, but in the end, I got it! I got a piece of paper and wrote down and the possible combinations and tried them out. After trial and error, I found out that you can in 17 minutes make all 4 members cross the bridge. Firstly, Rachel and Ben will cross. As the two will walk at the rate of the slower person they both take 2 minutes to cross. Next, Rachel walks back which takes 1 minute, and George and Yvonne take 10 minutes to cross. Lastly, Ben takes the torch and gets Rachel (takes 2 minutes) and they both travel back in another 2 minutes which brings the total to 17!