There are 4 different original lett

There are 4 different original letters to mail to the post office box, which contains all 6 Cabinet the probability that individual letters don't leave repeat how much equal Cabinet.

ผลลัพธ์ (อังกฤษ) 2:

There are 4 different original letters to mail to the post office box, which contains all 6 Cabinet the probability that individual letters do not leave repeat how much equal Cabinet.