I am truly sorry that my lectures and problem solving are not as perfect as you wish. I am correcting typos and mistakes to make them as perfect as possible.
1. If P-value > a=level of significance, the correct answer should be "Do not reject the Null hypothesis".
2. I noticed that there were few instances that I used invorm rather than nomalcdf.
3. I admit that there are typos in lectures.
Sorry for the inconvenience.