[填空题]
A tsunami of wavelength 250 u /hfhy,.j5ye/ .w0oqr9 obeojf34qg km and; wttjvmxc,9 * velocity 750 km/h travels across the Pacific Ocean. As it approaches Hawaii, people observe an unusual decreasxjw* tctm,v9;e of sea level in the harbors. Approximately how much time do they have to run to safety? (In the absence of knowledge and warning, people have died during tsunamis, some of them attracted to the shore to see stranded fishes and boats.) min
