Lead hydrogen arsenate, an inorganic insecticide used against the potato beetle, is produced by the following reaction:
$$
\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{3} \mathrm{AsO}_{4}(a q) \rightarrow \mathrm{PbHAsO}_{4}(s)+\mathrm{HNO}_{3}(a q)
$$
Balance this equation.