I've already almost got my first draft for the Heroic Fantasy story done. O_o (It does help that I'd already had an idea I was poking at yesterday that happened to fit the bill perfectly.)
I'm going to write the Time Travel story next, because I more or less know exactly what I want to do there. (I should note that this amuses me greatly, because this is the story I expected to be the hardest to figure out. That just means I thought at it really hard until I realized what I wanted to do, though.)
Lost Worlds is a little more difficult, but I do have a setting that I can use. I just need to solidify who the main character is and work out fine details of the plot.
I expected Supernatural Horror to be the easiest story to work on, since I enjoy the genre very much, but I find myself stumped because I have no idea as to a specific story yet. Just a driving notion that I VERY MUCH WANT TO WRITE A STORY IN THIS GENRE. ...Stupid brain.
I'd forgotten how good I was at writing from prompts in college. Yesterday, I was terrified that I wouldn't be able to do this. Today, I think it honestly won't be that hard and I can have all four first drafts done within a week if I apply myself, which gives me three weeks to rest and/or edit. The real answer to how difficult this will be probably lies somewhere in the middle.