Pedalling my buns off....

So here is my question...What is a respectable time (miles/minute) for bicycling? I took off and rode 6.8 miles in 30 minutes. I have no idea what I should be striving for!  I could probably push it faster but this was with no running prior to taking off on my bike. I did put in a 12 hour shift which I spent most of it on my feet.