Doppler Effect Help please, I dont think I'm right

Consider the diagram below of a very fast car with its horn blowing. An observer at A hears an apparent frequency of 474 Hz, whereas an observer at R hears an apparent frequency of 338 Hz. The air temperature is 24.9° C.

A. What is the speed of sound in air at this temperature?
B. What is the velocity of the car?
C. What is the actual frequency of the horn?

For A I calculated it as 345
For B I calculated it as 98.2
For C I calculated it as 342 (I know this is wrong)

The only answer Im sure of is A, can you help me pleaseeee? Thankksss!

Since the temp you found is right, then…For observer A, whom the source is approaching, the observed frequency is:

f(A) = f(s)[v / v - v(s)]

For observer R, the sign in the numerator changes to plus because the source is receding:

f(R) = f(s)[v / v + v(s)]

Solving each equation for frequency of source, f(s), because this remains constant, and setting them equal, we are left only with the unknown velocity of the source. We get:

f(A)[v - v(s)] / v = f(R)[v + v(s)] / v
v(s) = v[f(A) - f(B)] / [f(B) + f(A)]
= 345m/s(474Hz - 338Hz) / (338Hz + 474Hz)
= 57.8m/s

The C part is easy, because you can put the source velocity into either of the first two equations to get the actual source frequency. I’ll leave it to you to work it, but the result I get is 395Hz

Hope this helps.

How did you get the velocity?

you need more data.