3-8: 4 SEE ANSWER

Answer: fc1= 147 Hz, fc2= 293 Hz, fc3= 146 Hz

The first combination tone is found with the formula f2 - f1 = 597 Hz - 440 Hz = 147 Hz.

The second combination tone is found with the formula 2f1 - f2 = 2 (440 Hz) - 587 Hz = 293 Hz.

The third combination tone is found with the formula 3f1 - 2f2 = 3 (440 Hz) - 2 (587 Hz) = 146 Hz.