Consider a person riding a bike. Let's say that they start out from rest and reach a speed of 10 meters per second by 1 second, 15 meters per second by 2 seconds and 18 meters per second after 3 seconds. What is the person's acceleration during this time period?
a) 2 meters per second squared
b) 5 meters per second squared
c) 8 meters per second squared
d) 10 meters per second squared