I am not modest because I am not good at math. Tell me, you'd better listen to the teacher. The topic says at least once a hundred years, indicating that the frequency should be below 0.0 1. The frequencies corresponding to 48 meters and 49 meters are 0.02 and 0.0 1, and the unqualified ones are excluded. 50 and 5 1 have the same frequency, both of which are 0.005, which meets the requirements, but it is 50 because it is the lowest water level.