A car starts from rest with a velocity given by v=kt^3 where k is a constant. The expression for the distance traveld by the car from its position at t=0 is:

a] 3kt^3
b] kt^3
c] 6kt
d] kt^4/4

The distance is obtained by integrating the velocity with respect to t, and noting that d(0)=0 (initial position).