Who is Aufabu? Is he a man ?

No, it is a rule. The aufbau principle, from the German Aufbauprinzip, also called the aufbau rule, states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. For example, the 1s subshell is filled before the 2s subshell is occupied.

thats a little if u want the answer just look it up on google thats what i do haha : )

6.4 cm (max) - 25 cm (min)