No one can tell you the file size because JPG compression will be different for every photo. Pictures of thousands of blades of grass will take up more space than a close up of a face. Generally they'll be in the 2 - 4 MB range, I think. But that's just a rough estimate.
The iPhone 4s takes 8 Megapixel 3264x2448 images (sizes vary). You can get apps like Camera HD+ that will allow you to take shots using various megapixel ratings.
Looking at a series of photos I have taken they vary from 1.7mb - 3.6mb.
Night time grainy photos will be the largest. As stated above complicated detailed photos compress worse so the files are largest. The grain/noise in low light photos is "detail" as far as the compression goes.
Huh? what is impossible, I am trying to figure out what you mean....
But I do understand what everyone has mentioned, I will have to take some shots to see, as I was going to get a LifeProof Case to use underwater, but I am not sure what the photos will look like.
Printable size? You can print and 8x10 if the exposure is good. One could go larger too, but quality of said print from this tiny sensor would ultimately be up to you to decide.
MB Size will range from 1.5 to say 4mb depending on the image/ISO, etc....