25Hz.
Frequency at output of a counter = Input frequency/(mod number).
Frequency at W = 2MHz/25 = 80000 Hz. (Mod 25)
Frequency at X = 80000Hz/16 = 5000 Hz. (Mod 16)
Frequency at Y = 5000Hz/25 = 200Hz. (Mod 25)
Frequency at Z = 200Hz/8 = 25Hz. (Mod 8)