Philosophy (Predicate Logic Error)

A. What is the specific error in the following proof? How do we fix the error to make the proof correct? 

1. (x)(Fx > Gx)
2. (x)Fx               /(x)Gx
3. Fa > Ga           UI, 1
4. Fa                    UI, 2
5. Ga                    MP, 3,4
6. (x)Gx                UG, 5 

B. What is the specific error in the following proof? How do we fix the error to make the proof correct? 

1. (x)(Fx > Gx)
2. (3x)Fx            /(3x)Gx
3. Fa > Ga           UI, 1
4. Fa                    EI, 2
5. Ga                   MP, 3,4
6. (3x)Gx             EG, 5 

C. What is the specific error in the following proof? How do we fix the error to make the proof correct? 

1. (x)(Fx > Gx)
2. (3x)Fx                /(3x)Gx
3. Fx                       EI, 2
4. Fx > Gx              UI, 1
5. Gx                      MP, 3,4
6. (3x)Gx                EG, 5