Also, a primer on The Art of Discounting puzzle. (Maybe add more junk later if I ever feel like it.)
If you already bugged it, I would recommend starting a new game. At night, ask mom for a computer. Go to your room and look at the computer. At noon, go to Spare Classroom and get the USB. Go to your room and plug it in the computer. On the next day, you can turn on the computer. Go to the Lectures and DON'T GET LOCKPICKING, and DON'T GET STEALTH. Immediately work on the Discounting Puzzle.
Try to complete the top row first, because the sky is easiest to tell apart. For the hills and trees, you can generally tell by the color difference, tree line, or fogginess level. The bottom part is a bit of guess and plug-until-it-fits.
You can get Lockpicking and Stealth after either completing Discount or moving all the pieces away from the upper left side.