Dolores Said:

I need some help writing a business proposition letter, can someone help me out?

We Answered:

I think that you need to state like in your question what they could gain and back it up with a fact. But depending on what you are representing you have to think all angles because they are probably too. You also probably should state those as well within your proposition, if you don't get the chance to have a q&a session with them...
Good Luck