I with the Doppler Effect - I solved 2/3 parts of the problem

[mmutinoi]

I solved for parts and a and b of this problem and need someone to check the answers for me and help me with part c.
A) 467.5 Hz
B) 5.45 m/s

Jane is standing on the platform waiting for the train. The train approaching the platform from the north at 20 m/s blows its whistle when it is 100 m away from Jane. John, running towards the platform from south, is 50 m away from Jane when the whistle is blown. The frequency of the whistle when the train is at rest is 440 Hz, and the speed of sound in air is 340 m/s.

a) What frequency of sound does Jane hear?
b) John hears a frequency of 475 Hz. How fast is he running?
c) What is the difference in sound level between Jane and John assuming the whistle to be a point source of sound?

 

[jbsteele]

A) 467.5 HzB) 5.45 m/sC) The difference in sound level between Jane and John is determined by the inverse-square law of sound, which states that the intensity of sound decreases in proportion to the square of the distance from the source. Therefore, the difference in sound level can be calculated as: Sound Level Jane - Sound Level John = 10 log(100^2 / 50^2) = 10 log(4) = 12 dB