1. Ring A - a benzene ring numbered 1 to 6.
   - C-1 carries the only ring-ring bond, joining to atom 1 of Ring B (see below). 
   - C-3 bears a methyl group (-CH3). 
   - C-4 bears a methoxy group (-O-CH3).  
   - C-2, C-5 and C-6 carry only hydrogens.

2. Ring B - a separate six-membered aromatic ring (pyridazine) attached to Ring A through its atom 1.  
   Number this ring 1 to 6 starting at the carbon bonded to Ring A and moving sequentially.  
   - Atom 1: carbon bonded to Ring A.  
   - Atom 2: unsubstituted carbon.  
   - Atom 3: carbon bearing an exocyclic amino group (-NH2).  
   - Atom 4: carbon doubly bonded to an exocyclic oxygen.  
   - Atom 5: nitrogen that carries an chain substituent described in section 3.  
   - Atom 6: nitrogen completing the ring back to atom 1.  

3. Chain substituent on Ring B (attached to Ring B atom 5):   
   - a four-carbon chain where the third carbon (counting from the nitrogen) is secondary and bears a methyl branch.

Stereochemistry: no chiral centers and no E/Z double-bond constraints.