Hello. I would like 2 of the firewood bundles, 2 of the food and one of the water. You can have the rest. 
Hello I need 2 fire wood and you can have 2 food and 2 water
I can have the other firewood. It gets very cold at night, so I really need some extra firewood. 
I can give you 3 firewood if you give me 3 food and 2 water
I do need some extra food, as we will be hiking a lot. What about I get 3 firewood, you get 2 food and 3 water? 
i cannot sorry
Why not? 
I need 3 food if i give 3 wood
Like I said, I need some food or we will have a terrible trip. 
ok i will give you 2 firewood for 2 food and 2 water 
Just to be clear, your offer is I get 2 firewood and 1 food and 1 water and you get one firewood and 2 food and 2 water?
yes
Alright, that is fine.