From the chat history, get a list of decision variables (only those present in the chat history), add a column for time to spend in the city and cost.
In the context of travel, the variables could be
Example:
```
Chat history: 
I would like to travel to France for 7 days, my budget is $700. I like museums and history, I also love hiking.
Variables: Museums, History, Hiking, Time (days), Cost ($)
```
Chat history: 

New request:
I want to plan a trip to Germany for 16 days, with a budget of 1300 euros. I love museums and nature.

Variables: