A signature written with carbon pencil weighs 1mg.What is the number of carbon atoms present in signature?

Question

$\begin{array}{1 1}(a)\;6.02\times 10^{20}& (b)\;0.502\times 10^{20} \\(c)\;5.02\times 10^{23}&(d)\;5.02\times 10^{20}\end{array}$