_ b c

(a)  

_ c d

(a)  

_ f g

(a)  

_ g h

(a)  

_ h i

(a)  

_ e f

(a)  

_ j k

(a)  

_ k l

(a)  

_ l m

(a)  

_ i j

(a)  

_ p q

(a)  

_ n o

(a)  

_ m n

(a)  

_ o p

(a)  

_ r s

(a)  

_ s t

(a)  

_ t u

(a)  

_ q r

(a)  

_ v w

(a)  

_ x y

(a)  

_ y z

(a)  

_ u v

(a)  

_ w x

(a)