Answer:
The Doppler effect can be calculated by:
f' = ((v - v0)/(v -vs))*f
where f is the frequency, v is the velocity of the wave, v0 is the velocity of the observer and vs is the velocity of the source.
But the observer and the source move at the same speed (bot cars have the same velocity), so here we will not see the doppler effect the relative velocity between the cars is 0m/s.
This means that the frequency that will be heard by the speeder is 475hz
