Hello Julien, 
your domain should be this : 
 &, A, '|', '|', &, B, C, &, D, E, &, F, G
To get it, you need to follow this step by step: 

Considering  : 
Q = (B & C) | (D & E)
A & ( (B & C) | (D & E) | (F & G) )  =  A & ( Q | (F & G) )
SO it would be : 

&, A,  Q | (F & G)
&, A, |, Q, (F & G)
&, A, |, Q, &, F, G      (M)

Now for Q it will be  : 

Q = (B & C) | (D & E)
|, (B &C), (D & E)

|, &, B, C, &, D, E
Take that and replace it in (M), you will get : 

&, A, |, |, &, B, C, &, D, E, &, F, G

Upvote if this helps!
Thank you