9 minutes and 10 seconds per mile.
That is a very comfortable and highly efficient pace.
Unless the marathon distance breaks down your legs, I think most 40 year old females who jog five miles, three times a week, could probably turn in a time very close to that.
I remember,from somewhere, if you can get to where you can run 13 miles you can run a marathon.
Personally, I prefer a bike.
Can go a lot further faster.
And pack enough to go camping for a week.