Hi! What sort of packages are you looking for today?
Hi there! I am looking to have 3 packages of firewood, 2 packages of food, and 1 package of water please. 
Oh we have similar priorities 🙂I am also interested in getting firewood, because I have a condition that makes me very cold, colder than the average person, so I need to make sure I have enough for the trip. Why do you want food
That make sense. I need firewood though too because I have an autoimmune disease. When it flares up - when it gets too cold - I get very sick and have to go to the hospital. I need to make sure I have enough for the trip as well. I need food to keep my metabolism up so I can make sure my disease stays in check. Why do you want food?
That makes sense . I have a friend coming with me on the camping trip, and she also needs to eat, so I'd like to get an extra package of food if possible. 
Okay that would be fine. If I can have 3 packages of firewood, you can have 2 packages of food. Does that work?
That does not work for me. I need at least one package of firewood. I'm sure you understand, because it seems like we have medical conditions with similar effects. You can take all of the water if I can get 2 packages of food and 1 of firewood. Does that work?
I do understand. That will work for me. 
Could you tell me about why you want water? 
I want water so I can keep hydrated during this camping trip. It's important for me to drink bottled water vs. getting water out at camping as it may flare up my disease. 
Oh interesting! I have a device that allows me to drink pond/stream water by cleaning it, so water isn't as important to me.