What's a reasonable routine?

newmom_2012

I just finished C25K last week, and I'm struggling to figure out what my routine should be now. I'm very very slow (5k takes me about 45 minutes) I'd like to increase my runs to 4x/week instead of 3x/week. What I don't know is how many km I should be doing. This week I did 4 runs for a total of 15.4km, previously the most I did was 9.5km in a week. Each day I set out to do the full 5k and twice I didn't end up finishing, I realized that I would be doubling the number of km in a week I was doing and maybe I should pace myself a little bit more.

So I guess my question is what is a reason goal as far as how many km in a week should I be running, and what is good break down? A couple longer days, and a couple shorter days, one long and three short or vice versa? 5k is still pretty challenging for me, so my goal at this time is to get more comfortable with 5k, while maybe increasing my speed a little bit.