I'm sorry, but can you explain how that particular input (list of words you provided in your post) maps to output (4)?
If those were just the examples of the format in which you'll give your challenges, I think it'd be much better if you explained the challenge as clearly as possible, and gave working example.
Here, for example, the number of "tee" in the word Steem may mean "how many words containing tee there are in the input", or "how many words that mean Steem (i.e. with different case) that also contain tee there are in the input". In other word, it's ambiguous - or it's just me having issues with trying to understand it.
RE: [Idea] Who would like a series on a Python programming challenges posted weekly?