Commute by bike

The day before yesterday, my pass for JR was finished. So, I am commuting by bike from yesterday . It takes about 75 minutes when I commute by JR and city train. On the other hand, it takes about 30 minutes by bike.
When I reach to Port Ujina, I can study on the seat about 30 minutes. But I had studied in the train too. So I don't know which is better for me.