Answer
440 Hz. 660 Hz.
Work Step by Step
As seen on page 395 and in Figure 21.5, the second harmonic is at two times the fundamental frequency, or $2 f_{o} = (2)(220 Hz) = 440 Hz$.
The third harmonic is at three times the fundamental frequency, or $3 f_{o} = (3)(220 Hz) = 660 Hz$.
The fourth harmonic is at four times the fundamental frequency, or $4 f_{o}$, and so on.