Answer:
26.6 min
Explanation:
The speed of a wave is equal to the frequency (number of waves per second) times the wavelength (length of the wave). The period of a wave (seconds per wave) is the inverse of the frequency.
v = fλ
8000 m/s = f (2 × 6.38×10⁶ m)
f = 6.27×10⁻⁴ Hz
T = 1/f
T = 1 / (6.27×10⁻⁴ Hz)
T = 1595 s
T ≈ 26.6 min