Your question is Bridge Crossing Puzzle. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
There are four people who need to cross a bridge at night with one flashlight; they have different speeds (1, 2, 7, and 9 minutes). How do you get everyone across in the fastest time?