In terms of the absolute minimum just to conduct operations off the east and west coasts, six conventional boats would probably be sufficient. That would enable you to establish an operations cycle on either one. That would enable the continuous presence of a submarine able to deploy to just off our coasts.
If we bring in the Arctic or if we are looking at sending submarines abroad, we would need to double that number because of the transit times to get submarines to and from station.
However, if we were to go to a nuclear option, we could also go back to a six-boat number, simply because the speed with which nuclear boats can travel under water, up to 25 knots or more, means that they can get on station very quickly. To give you an example, it took about 80 days for Chicoutimi to cross over from Esquimalt to Yokosuka in Japan. A nuclear boat could probably do that in under a week.