The net charge of the asteroid is
[tex]Q=-126 C[/tex]
with a negative sign since it is a net negative charge.
The charge of one electron is
[tex]e=-1.6 \cdot 10^{-19} C[/tex]
In order to find what is the excess of electrons on the asteroid, we must simply divide the net charge in excess on the asteroid by the charge of a single electron, and we find:
[tex]N= \frac{Q}{e}= \frac{-126 C}{-1.6 \cdot 10^{-19} C} =7.87 \cdot 10^{20} [/tex]
