Which of the following is an incorrect application of Leibni

Which of the following is an incorrect application of Leibniz\'s law?

inferring Fa Fb from Fa Fa and a = b

inferring (x)(Fx Fb) from (x)(Fx Fc) and b = c

inferring ($x)(Fx Fx) from ($x)(Fx Fy) and x = y

inferring (x)Fx Gb from (x)Fx Gz and z = b

Solution

inferring (x)Fx Gb from (x)Fx Gz and z = b is coreect answer