Nylon is prepare first in ___

I think answer should be 10 please give me brainlest I hope this helps let me know if it’s correct thanks okay bye thanks

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.