If you would like, John, I'll jump in on that one.
I think as opposed to focusing it on nuclear, the real piece, and the approach the navy normally takes with respect to developing the statement of its requirement, is on the requirement that we're trying to get there. You've touched on it. People often say nuclear because they're talking about the ability to operate under ice; air-independent propulsion, if you will. There are a number of potential methodologies for delivering that, with more advanced ones growing each day in addition to the nuclear option. Certainly I would say that this will be a consideration we need to have as we look at continuing the submarine service with follow-on classes.