Doppler Effect Question regarding wavelength changing

[Shahzad7317]

Homework Statement

A listener L hears the siren from a moving police car ,S, which is moving away from the listener with a speed of v = 20.0 m/s. The listener is moving at 10.0 m/s towards the car. There is a wind blowing with a speed of v(wind)= 10.0 m/s from S to L. The siren is emitting sound at a frequency (f) of 800 Hz. The velocity of sound in air is 343 m/s. Calculate the frequency (f') heard by the listener and the wavelength (λ) of that wave.

Homework Equations

f' = f(v +/- vD) / (v -/+ vS)
v = fλ

The Attempt at a Solution

Finding the new frequency is easy:

f' = (800hz)(343+10+ 10)/(343+10+20)
f' = 779 Hz. But now for finding the wavelength I'm confused.
I know it's λ = v/f'

but is it:
v = 343m/s (the speed of sound in still air)
v= 343+10 m/s (the speed of sound + the speed of the wind)
v= 343+10+20 m/s (the speed of sound + the speed of the wind + the speed of the source)
or something else?

Any help would be much appreciated.

 

[Simon Bridge]

The wavelength heard by the listener is the frequency of the sound divided by the speed the wave is passing the listener.

 

[Shahzad7317]

The wavelength heard by the listener is the frequency of the sound divided by the speed the wave is passing the listener.

My apologies, I put the wrong question (I had v = f/λ when it should be v= fλ); I fixed this up now.

But by your statement would be the last option I suggested? λ = (speed of sound + speed of wind + speed of source)/(new frequency)?