How many electrons must be removed from a piece of metal to give it a positive charge of $\;1\times10^{-7} \;C\;?$

Question

$(a)\;6.25\times10^{11}\qquad(b)\;6.25\times10^{19}\qquad(c)\;1.66\times10^{19}\qquad(d)\;3.125\times10^{11}$