How do I start this one? I need help with using the right formula.?

At rest, a cars horn sounds the note A (440 Hz). The car is driving east along a country road. There is also a bike cyclist on the road, traveling east at 1/4 the car’s velocity. The driver honks at the cyclist for whatever bewildering reason it is that drivers feel the need to honk at people getting healthy exercise. The cyclist hears the cars horn at a frequency of 415 Hz. What is the speed of the car? Is the cyclist ahead of or behind the car?