 Then "n"3 formula_2 5 and "n"3 ≡ 1 (mod 3).The only value satisfying these constraints is 1; therefore, there is only one subgroup of order 3, and it must be normal (since it has no distinct conjugates).Similarly, "n"5 must divide 3, and "n"5 must equal 1 (mod 5); thus it must also have a single normal subgroup of order 5.