Good time for biking?

I am in my third week of training (couch to Olympic) for an Olympic triathlon, which I will participate on 18 Sept. This is my first triathlon and I am not sure what good times are. I checked out last year's winners for the race but did not see individual breakdowns per event. I completed 25 miles today at a pace of 20 mph. Is this a poor or adequate pace for third week of training? What is a good time to aim for? I know my time will decrease once I hop on a road bike with clipless pedals (poor grad student with a mountain bike and running shoes ). Thanks for any input.

Victoria