Proof Writing & Problem Solving · Easy problem

A long proof consists of four lemmas $A$, $B$, $C$, $D$ and the main theorem $T$. Lemma $B$ uses $A$, lemma $D$ uses $C$, and $T$ uses $B$ and $D$; no other result uses another. The write-up must state each result after every result it uses. In how many orders can the five results be written?