Dear

Your offer to help us in our campaign to    [objective]
is greatly appreciated.  If everyone were to commit
themselves with the same level of enthusiasm you
expressed in your letter, we would undoubtedly have this
problem licked in no time at all.

We are sending you one hundred of our pamphlets to be
distributed to your personnel.  This will help us to
spread the word while keeping our costs down to a minimum.

Thank you again for your willingness to assist.