I recommend that you prioritize your work as follows.

• Complete 7b (The history portion of TicTacToe). This is pretty easy.

• Complete 8 (Reverse Polish Notation). This is also pretty easy. LYAH gives you the code.

• Complete 7c (Understand all of TicTacToe). This requires that you understand the most code. If you don't already have credit for 7a this will get you credit for it. The 7a grade will be based on the 7a schedule.

• Complete 9 (Heathrow-to-London Calculator). This requires that you write some of your own Haskell code based on code in LYAH. (Actually, it gives you most of the code. I've also posted my solution.) In that sense it is the most comprehensive project. This project is a version of shortest path. You can use a more general shortest path algorithm if you prefer. (Of course you must understand it and be able to explain how it works.)