How is each category from #$3$ usually classified $($variable or fixed expense$)$ in the United States?

Group of answer choices

Direct labor $-$ fixed expense, indirect labor $-$ variable expense, direct materials $-$ fixed expense, indirect materials $-$ variable expense, and overhead $-$ mixed expense

All are fixed expense

Direct labor $-$ variable expense, direct materials $-$ variable expense, and manufacturing overhead $-$ variable, fixed, or mixed depending on the expense

All are variable expense