This week, lecture 9 covered slides 1 to 23 and lecture 10 covered slides 24 to 39 of the lecture slides.
You should have learnt about defining and working with algebraic data types.
The reading for this week is chapters 13 to 14 of the textbook, pages 287 to 356.
Remember to keep up with the reading! The textbook covers things in more detail than the lectures and has exercises to help you learn. Try doing the easy exercises in the textbook before you attempt the tutorial exercises.