Default category on New Question by slug

I’m using Categories extension, and I think that when you Ask a new question being inside some category, the ask question form should have by default that category selected.

It could be just something as easy as have a slug like: /questions/category_name/ask that make happens that.

I’m not very into php, but I will try to do it. Advices accepted.

Thanks for the great work, just awesome.