python - Signal amplitude to FFT amplitude

I am using Python to generate a sine wave in order to cancel out part of a signal I'm analyzing. I would like the magnitude of this signal in the FFT to be equal to the magnitude of the signal that I want to get rid of. My questions are:

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  A. How does the amplitude of a signal translate to the amplitude of the resultant FFT?

  
  


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  B. Is there a way I can easily control the amplitude of an FFT using the amplitude of an input signal?

  
  

I can post my code if it helps.

This is the FFT of the signal I'm analyzing. I want the large amplitude at 1.4-ish(from the signal I generated) to be equal in magnitude to the large amplitude at 2.9-ish (the frequency I want to get rid of)