it is very urgent
Then again, who knows ....??
@OP: It would have helped if you posted the original and unabridged question rather than your interpretation of it. As it stands, your urgent question potentially remains unanswered (after nearly 12 hours) simply because we can only make guesses at what the real question might have been.
Did you read the reply?
Please use words and communicate the actual problem statement and why you are pursuing this problem. In particular, what class are you and and what is the name fo the chapter and unit you are working on?