What would my pension be?

I am doing a homework task at the moment, and I have to find out what my pension would be when I retire. I would be hoping to earn around �40,000 to �45,000 at the end of my career, and I should retire when I am about 65-67. I am male if that makes any difference? I need to know how much I would get paid a year. Thanks for your help! :)