没人能帮助我吗~?

Just go back to you textbook, the answer is obviously writen there. For example, the book "Investment Analysis and Portfolio Management"

yeah, i see. The purpose i posted this item is to ask does anyone have written similar eaasy before. if so, may i share the ideas and take it for reference if possible.

does it necessary to write an essay for such a question?

If you have the text books, it is easy to answer them. Just

read the text books and pick up the idea of the theory!