A Tidal Wave (Tsunami) of Wavelength 4 $\times$ 10⁵ M Travels at 200 M/s in the Open Ocean

A tidal wave (tsunami) of wavelength 4.8 $\times$ 10⁵ m travels at 200 m/s in the open ocean. The time between two successive incoming waves is

A) 0.21 $\times$ 10^-3 s.
B) 0.42 $\times$ 10^-3 s.
C) 24 s.
D) 20 minutes.
E) 40 minutes.