Calculate the frequency of the siren

[BioMechanical]

Homework Statement

A police car is moving towards the east at 34.0 m/s while sounding its siren. There is a wind blowing from the west with a speed of 15.0 m/s. A second police car is ahead of the first police car and is sounding its identical siren while moving towards the east at 32.0 m/s. A policeman in the first police car hears a beat frequency of 4.80 Hz between the two sirens. The speed of sound in air is 343. m/s.
Calculate
(a) the frequency of the siren;
(b) the beat frequency heard by the policeman in the second police car;
(c) the frequency from the siren of the faster police car heard by a person standing on the sidewalk between the two cars.

Answers
(a) 864.0 Hz
(b) 5.333 Hz
(c) 954.7 Hz

Homework Equations

f1=f(V-Vd/V-Vs)

The Attempt at a Solution

i think v=343-15
v=328m/s
Besides the above, I'm Clueless. Can someone help me out? (no solutions please)
Thanks guys

 

[Oberst Villa]

Homework Statement

A police car is moving towards the east at 34.0 m/s while sounding its siren. There is a wind blowing from the west with a speed of 15.0 m/s. A second police car is ahead of the first police car and is sounding its identical siren while moving towards the east at 32.0 m/s. A policeman in the first police car hears a beat frequency of 4.80 Hz between the two sirens. The speed of sound in air is 343. m/s.
Calculate
(a) the frequency of the siren;
(b) the beat frequency heard by the policeman in the second police car;
(c) the frequency from the siren of the faster police car heard by a person standing on the sidewalk between the two cars.

my first step would be the transformation into a reference frame that is moving with the same velocity as the wind. thereby you take care of the wind once and don't have to consider it during the further calculations. so the transformed velocities of the objects are:

first police car: 19 m/s
second police car: 17 m/s
person: -15 m/s