2

9

3

6

-4

(a)  

8

5

4

-3

6

(a)  

9

8

7

4

5

(a)  

2

3

5

-8

6

(a)  

9

8

-4

7

5

(a)  

6

9

8

3

-6

(a)  

5

8

-6

9

7

(a)  

4

1

-2

3

5

(a)  

6

9

-8

6

4

(a)  

2

3

7

5

-6

(a)  

9

8

6

-4

2

(a)  

5

6

-3

8

7

(a)  

4

7

-6

3

2

(a)  

1

4

7

-9

8

(a)