Which Rank is the Smartest, Private, Lt., General?

I was expecting something like the following joke:
The Commanding Officer of a Regiment in the U. S. Marine Corps was about to start the morning briefing to his Staff and Battalion and Company Commanders. While waiting for the coffee machine to finish its brewing, he decided to pose a question to all assembled. He explained that his wife had been a bit frisky the night before and he failed to get his usual amount of sound sleep.

He posed the question of just how much of sex was 'work' and how much of it was 'pleasure?'
The X.O. chimed in with 75-25% in favor of work.
A Captain said it was 50-50%.
The Colonel's Aide, a Lt., responded with 25-75% in favor of pleasure, depending on his state of inebriation at the time.

There being no consensus, the Colonel turned to the Private First Class who was in charge of making the coffee.

What was HIS opinion?

With out hesitation, the young Private First Class responded, "Sir, it absolutely has to be 100% pleasure." The Colonel was surprised and, as you might guess, asked why? "Well, Sir, began the Private First Class, "if there was any work involved, the officers would have me doing it for them."