I got myself a book after looking the advice from stackexchange, it has been so far helpful for me. But I got confused in this numerical given in the book.
The other method is this-: https://www.youtube.com/watch?v=VhoVH2wB9dc&t=1248s But the answers from two methods are different. i.e the transfer function from these 2 processes are different. I am confused. Which is right and which is wrong.