Suppose I have a waveform x(t);
where x(t) = 5 + 30cos(2000πt) + 10cos(6000πt) that is to be uniformly sampled for digital transmission, how do I calculate the bandwidth of this signal?

I reckon that it would 4000 Hz because we're subtracting the highest and lowest frequencies (6000-2000). Is this right?

However, the answer in my book says it's 3000 Hz. I do not understand how did they get this answer.

Thank you for reading

Suppose I have a waveform $x(t)$
where $x(t) = 5 + 30\mathrm{cos}(2000\pi t) + 10\mathrm{cos}(6000\pi t)$ that is to be uniformly sampled for digital transmission, how do I calculate the bandwidth of this signal?

I reckon that it would $4000 \textrm{Hz}$ because we're subtracting the highest and lowest frequencies $(6000-2000)$. Is this right?

However, the answer in my book says it's $3000 \textrm{Hz}$. I do not understand how did they get this answer.

Thank you for reading