Answer
The missing frequencies are 2, 6, 12 and 12.
Work Step by Step
The lower two frequencies must mirror the first two frequencies, therefore they are 2 and 6. We can get the peak frequencies by subtracting the known frequencies from the sum of them and then dividing it by 2 (because we are looking for 2 peaks). Therefore the peak frequencies: (40-2-6-2-6)/2=24/2=12. Therefore the missing frequencies are 2, 6, 12 and 12.
