For each of the following, decide if the expression is "always countable", "always uncountable", "sometimes countable, sometimes uncountable". for the "always" cases, prove your claim. for the "sometimes" case, provide two examples – one where the expression is countable, and one where the expression is uncountable.

At the "no mutants allowed" country farm, every sheep has 4 legs, every chicken has two legs, and all animals have only 1 head. asked to count how many sheep and chicken are in the fields, a farm boy reports back that there are 140 feet and 50 heads. how many sheep and chicken are there? there are sheep and chicken at the farm.