b,2c,3a

A

B

D

C,2a,3b

A

B

A

B

A

C

B,2c,3a

A

B

A

B

A

A

D

D

B,2c,3a

B

A

A

D

A,d

B

C

B,2c,3a

A

B,d

C

C

B

C

C,2b,3a

B,c

C

B,2d,3a,4c

B