Answer:Highest frequency  =618.89Hz
Lowest frequency=582.22Hz
Explanation:
  The linear velocity of a sound generator  is related to angular velocity and is given as 
Vs = rω  where 
 r = the radius of circular path = 1.0 m
ω is the angular velocity of the sound generator. = 100 rpm
1 rev/min = 0.10472 rad/s
 100rpm =10.472 rad/ s
Vs = rω 
= 1m x 10.472rad/ s=  10.472m/s
 A) Highest frequency  heard by a student in the classroom = Maximum frequency. Using the Doppler effect formulae,
 f max = (v/ v-vs) fs
Where , v is the speed of the sound in air at 20 degrees celcius =
343 metres per second 
vs is the linear velocity of the sound generator=10.472m/s
fs is the frequency of the sound generator= 600 Hz 
 f max = (343/ 343 - 10.472) x 600 
=343/332.528) x600 
=618.89Hz
 
B) Lowest frequency  heard by a student in the classroom = Minimum frequency 
 f min = (v/ v+vs) fs
(343/ 343 + 10.472) x 600 
=343/353.472) x 600 
=582.22hz