Two particles move along the same straight track with position functions sA(t) and sB(t), measured in meters, where t is in seconds. To determine the instant at which the particles occupy the same point on the track, which of the following equations must be solved?
a) sA(t)−sB(t)=sA′(t)
b) sA(t)=sB(t)
c) sA′(t)=sB′(t)
d) sA′(t)=sB(t)