Section ExponentAbelem.
Variable gT : finGroupType.
Implicit Types (p n : nat) (pi : nat_pred) (x : gT) (A B C : {set gT}).
Implicit Types E G H K P X Y : {group gT}.
Arguments exponentP {A n}.
Arguments nElemP {n G E}.

Lemma p_rank_Hall pi p G H : pi.-Hall(G) H -> p \in pi -> 'r_p(H) = 'r_p(G).