Mass planetary formation calculation?

[black_hole]

Homework Statement

Compute the mass of volatile material (specifically just H and He) not accreted by the Earth. Assume the mass accreted by the Earth is 7e23 kg. How does the mass of the missing volatiles compare with the actual mass of the Earth? Use the following table:

Principal Constituents of Sun and Solar nebula:
(Relative to number of atoms in the Sun)
Hydrogen 92.1 %
Helium 7.8 %
Oxygen 0.061 %
Carbon 0.030 %
Nitrogen 0.0084 %
Iron 0.0037 %

I'm confused what the questions want me to do? What assumptions am I supposed to be making? What do these things have in common?

Homework Equations

The Attempt at a Solution

 

[Borek]

I suppose the question can be reworded to something like "In what mass of the initial nebula there was enough metals (in astrophysics sense) to create Earth".