theorem :: AUTALG_1:16

for I being set
for A, B, C being non-empty ManySortedSet of I
for F being ManySortedFunction of A,B
for G being ManySortedFunction of B,C st F is "1-1" & F is "onto" & G is "1-1" & G is "onto" holds
(G ** F) "" = (F "") ** (G "")