Word problem

[blobo]

Hello, I came across with a word problem in Algebra 1 book which i cannot seem to solve. I think its more of a resoning/logical problem than algebra.
Please help me solve it. Well first of all I just tried it the "trial and error" method, with no success. I assume there must be a more "formal" way, or some sort of method which I am unaware of to solve these kind of problems.
The problem is the following:

3 men with a bag of gold each, worth 8000, 3000, 5000, must get across a river. Their boat only allows for two men, or a man and a bag to cross at a time. They don't trust each other, so they have agreed not to stay alone, either on shore or on the boat, with more value of gold than they are worth (i.e. the man owning the 3000 gold bag could never stay alone with the 8000 bag, but the man who owns the 8000 could stay alone with the other two bags). In what order must they cross so to get to the other side of the river with their bags, in no more than 12 crossings (if the return is counted as a crossing).

This problem is obsessing me, pleas help!

 

[blobo]

Oh, I guess I have to show some of my work.

3= man 1 5 = man 2 8 = man 3
3g= 3000 gold bag 5g = 5000 bag 8g= 8000 gold bag

1. 3 crosses with 3g
2. 3 returns
3. 8 crosses with 5g
4. 8 returns
5. 3, 5 cross
6. 3 returns with 3g, 5 stays with 5 g - after this nothing seems to work,

 

[Denis]

A has 8000, B has 5000 and C has 3000; [] = other side

9 crossings will do it:

1: A crosses with 8000
2: A returns [8000]

3: A crosses with 5000
4: A returns [8000, 5000]

5: A crosses with 3000
6: A returns [8000, 5000, 3000]

7: A crosses with B
8: B returns [8000, 5000, 3000, A]

9: B crosses with C [8000, 5000, 3000, A, B, C]