This should be interesting. According to the race results from last week if you broke 20 minutes you would have placed 27th out of 959 runners. Only 4 guys broke 18 minutes and I am sure all 4 probably are serious amateur runners that train all the time. I don't know what kind of shape you are in and I have never seen you run, so I wouldn't take that bet. All I am going to say if you can finish in the top 3% of 5k race with no training you are a naturally gifted runner.