The quantity of carbon atoms in the pencil mark amounts to 3 x 10^17. Given that the atomic weight of carbon is 12.01 amu, it follows that 12.01 g of carbon contains 6.022 x 10^23 atoms. Thus, we can set up the equation: 12.01 g carbon/ 6.022 x 10^23 atoms (3 x 10^17 atoms) (12.01 g carbon/ 6.022 x 10^23 atoms). By canceling out the atoms, we have (3 x 10^17) (12.01 g carbon/6.022 x 10^23) and then completing the division and multiplication yields 6 x 10^-6 g of carbon. Therefore, the mass of the pencil mark is 6 x 10^-6 g.
