a cyclist travelling at 8 m/s^-1 observes a a car just beginning to accelerate uniformly 40 m distant. if the cyclist speed remains constant he can just catch the car. find the acceleration of the car

trying to solve this using uvast equations. cyclist u=8 v=8 s=40+s a=o t=t car u=0 s=s a=a t=t there are 3 variables here so i must be missing something