The year is 2029, and, as predicted, robots have taken over the world. You are given the task to come up with a communication protocol that the robots won’t be able to understand. You think back to the good old college years and think, "I sure am happy I took EE 202!" You know the robots process audio with an ADC using fs = 8000 Hz. Your idea is to use a variety of tones that will sound the same to the robots, so they won’t be able to interpret the meaning. You decide that one of your tones will have a frequency of f0 = 2000 Hz. What are 4 other frequencies that will be indistinguishable from f0 to the robots?