DEAR CRABBIT: synopsis for a trilogy?

Dear CrabbitI read 'Write A Great Synopsis' ( which I thoroughly enjoyed). I have a question regarding the submission. 

What of a trilogy? Do I include the synopsis for all three books and take three times the length to give the full outcome of the novel, or do I simply give the synopsis to the first book and no conclusion? Is it presumptious to give the synopsis for all three books, will it be