I've added 6 new videos to those available via the class website. Three of them are in Part 5 and three are in Part 4. None of these are essential for the homework assignments or for the tests. They're just to provide additional worked examples of the techniques that have already been introduced in other videos. The new ones in Part 5 are in place early enough that they will provide additional examples while you are preparing for the Part 5 test (which begins on April 6), and the new Part 4 videos you might find useful in reviewing for the final exam (which begins on April 27 which is about a month from now).