I have 2 questions I can't solve. I am Stuck.

1. A person with very good musical pitch listens to a guitarist on a moving stage play a high A (880 Hz) while the stage is moving away at 4.0 m/s on a cold day, 0 °C. What frequency does this person hear? If they can discriminate 0.25 Hz can they tell the difference between this note from a moving guitarist and a stationary guitarist?

2. Find the frequency of these modes if the air temperature 20 °C. A guitar string 1.3 m long with a wave speed of 66 m/s.