What is the chemical formula of ammonium sulfate?
NH4(SO4)2\text{NH}_4(\text{SO}_4)_2NH4(SO4)2
(NH4)2SO4(\text{NH}_4)_2\text{SO}_4(NH4)2SO4
NH4SO4\text{NH}_4\text{SO}_4NH4SO4
(NH4)2(SO4)3(\text{NH}_4)_2(\text{SO}_4)_3(NH4)2(SO4)3