According to the values given in your question, solution is as follows:
Charge on each copper atom=29 C
Total charge on the
copper ball
=29×4×10^23
=116*10^23 C
Thus,the number of electrons on the copper ball
=116*10^23(Since it is initially uncharged)
9.6 micro coloumbs=
9.6*10^-6
Number of electrons in
9.6*10^-6 coloumbs
=Q/e
=9.6*10^-6/1.6*10^-19
=6*10^13
This is the number of electrons to be removed
So the fraction of electrons to be removed is given by
6*10^13/116*10^23
=.051*10^-10
=51*10^-13