How does your Skeletal and Muscular Systems work together? Muscles move your bones
Bones move your muscles
Heart pumps blood throughout the body
Your bones protect your muscles

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.