An ultramarathon race is 421.95 km in length. Oliver knows his average speed for his previous races is 14.12 km per hour. For the next ultramarathon he will run for 15 hours per day. (a) Estimate how many days Oliver will take to complete the ultramarathon. (3) Oliver trains for the ultramarathon. The average speed he can run. It is now 15.27 km per hour. (b) How does this affect your answer to part (a)?