Answer
880 Hz. 1320 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 $2 f_{o} = (2)(440 Hz) = 880 Hz$.
The third harmonic is at three times the fundamental frequency, or $3 f_{o} = (3)(440 Hz) = 1320 Hz$.
The fourth harmonic is at four times the fundamental frequency, or $4 f_{o}$, and so on.