To solve this problem we will apply the concepts related to the Doppler effect. The Doppler effect is a physical phenomenon where an apparent change in wave frequency is presented by a sound source with respect to its observer when that same source is in motion. Mathematically it can be described as
[tex]f_d= f_s \frac{(v+v_d)}{(v-v_s)}[/tex]
The meaning of each of these variables is,
[tex]v_d=[/tex]Velocity of detector
[tex]f_s[/tex]=Frequency of wave emitted by source
[tex]v_s=[/tex]Velocity of source
v=Velocity of sound wave
[tex]f_d[/tex]=Frequency received by detector
Replacing we have that,
[tex]f_d = 798(\frac{(343+30)}{(343-30)})[/tex]
[tex]f_d=950 Hz[/tex]
Therefore the correct option is e. 950Hz