Dear

Your offer of help is truly appreciated at this time.
I believe if we can get our cost estimates down, we
should be able to have this proposal ready to submit
by the June 1st deadline.

I know that by taking you up on your kind offer, we
will both be burning the midnight oil for the next
week and a half, but I really doubt that I will be
able to complete this within the time limit without
your help.

Thank you very much.