Hi, I have question about the following attachment.

I have to sketch ACF of the output response.

I know that I have to cross multiply and sum the terms to get the output sequence. I have followed through examples and I cant get it working and I am not sure where am I going wrong. Can someone shed some light please?

I have worked out j(m) as 1,-4,6,-4,1

i now need to work out output sequence and not sure how