Speeding ticket help?

I just got a speeding ticket for 72 at a 45 expressway, but is impossible since it was a heavily traffic area going to work and for going on a ping lane for a few seconds because a slow car was merging to expressway and the car on the left of me was almost to the side of my car. I know I sped but this is exaggerating. I think the cop was pissed that I wanted to pull over to my work's parking lot because it was around the corner. I want to fight the speed, but not say not guilty because I actually did speed, but to reduce my ticket. Tell me the process. I can also go to traffic school and I live in Northern California. Do I go on the date on my yellow citation slip? Tell the judge guilty with explanation?