Given the set of outputs, find the fee sent 
    to our burn address.  This is always the third output.
    
    Return the fee and burn address on success as {'op_fee': ..., 'burn_address': ...}
    Return None if not found

def get_preorder_burn_info( outputs ):
    """
    Given the set of outputs, find the fee sent 
    to our burn address.  This is always the third output.
    
    Return the fee and burn address on success as {'op_fee': ..., 'burn_address': ...}
    Return None if not found
    """
    
    if len(outputs) != 3:
        # not a well-formed preorder 
        return None 
   
    op_fee = outputs[2]['value']
    burn_address = None

    try:
        burn_address = virtualchain.script_hex_to_address(outputs[2]['script'])
        assert burn_address
    except:
        log.error("Not a well-formed preorder burn: {}".format(outputs[2]['script']))
        return None

    return {'op_fee': op_fee, 'burn_address': burn_address}