Question

please solve the above question fast

Answer 1

if the fundamental frequency is 100 Hz, the nest higher frequencies will be 200 Hz, 300 Hz, 400 Hz, 500 Hz, and so on. If the fundamental frequency were 220 Hz, the nest higher frequencies  would be 440 Hz, 660 Hz, 880 Hz

so in your case it will be 400, 600, 800