In a Venn diagram with sets $A$, $B$, $C$, define regions as: $r_1 = A$ only, $r_4 = A \cap B$ only (not in $C$), $r_5 = A \cap C$ only (not in $B$), and $r_7 = A \cap B \cap C$. Given $|A| = 25$, $r_4 = 3$, $r_5 = 3$, and $r_7 = 5$, find $r_1$.