A boy in a wagon starts from a rest position and then goes down a straight ramp, gaining speed with uniform acceleration as he travels. In 6.00 s, he is traveling at 4.2 m/s.

a) The acceleration is 0.7 m/s²
b) The acceleration is 0.5 m/s²
c) The acceleration is 0.3 m/s²
d) The acceleration is 0.2 m/s²