How many c-13 atoms are present, on average, in a 3.×104-atom sample of carbon?

0.00107 * 24000
= 26

I think this is right, but im not sure.

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.

C) the increase in atmospheric pressure pushes the walls of the balloon outward thus making it  is the answer.hope i you.