for A, B, C1, C2 being category
for E1 being Functor of (C1 [x] A),B
for E2 being Functor of (C2 [x] A),B st E1 is covariant & E2 is covariant & C1,E1 is_exponent_of A,B & C2,E2 is_exponent_of A,B holds
C1 ~= C2