Chapter 4, Problem 68QP

What is the empirical formula of each of the following compounds?

$\begin{array}{l}\left(\text{a}\right){\text{ As}}_{\text{4}}{\text{O}}_{\text{6}}\\ \left(\text{b}\right){\text{ H}}_{\text{2}}{\text{S}}_{\text{2}}\\ \left(\text{c}\right){\text{ CaCl}}_{\text{2}}\\ \left(\text{d}\right){\text{ C}}_{\text{3}}{\text{H}}_{\text{6}}\end{array}$