How do I plot the line of the mean value on the same graph?

That title may not have fully conveyed my question, but here it goes.. I've created 3 random column vectors and plotted what they all look like on top of each other with this code:

c1=randn(30,1)*50; c2=randn(30,1)*50+300; c3=randn(30,1)*50+600; d1=[c1 c2 c3];

plot(d1) hold

Now I would like to plot lines which are the min, max, and mean of c1, c2, and c3 respectively. I've tried entering:

plot([0:30],mean(c1),'b')

but this only gives me 30 points and doesn't give me the option to use any line specifications, please help.