Six weeks is more likely, & offspring average more like six or eight, though perhaps less from younger females. Not "in nature" either, as most young bunnies are eaten by something, and they cannot breed all year. Could only happen where indefinite amounts of food and space are available. (You could try the experiment in, say, a really big open country with no native rabbits -- I know, what about Australia...?). Real ecology is not quite that simple...
Sounds like a carefully worked example, rather than a real situation -- but pretty well within what is physically possible.