XML DB :: Find Size Of Table With XML Type Column Store As Binary XML

I have a table with structure as:

CREATE TABLE XML_TABLE_1
(
ID NUMBER NOT NULL,
SOURCE VARCHAR2(255 CHAR) NOT NULL,
XML_TEXT SYS.XMLTYPE,
CREATION_DATE TIMESTAMP(6) NOT NULL
[code].....

- So HOW do I find the total size occupied by this table. Does BINARY storage work as LOB storage. i.e. I need to consider USER_LOBS as well for this. OR foll. will work

select segment_name as tablename, sum(bytes/ (1024 * 1024 * 1024 )) as tablesize_in_GB
From dba_segments
where segment_name = 'XML_TABLE_1'
and OWNER = 'SCHEMANAME'
group by segment_name ;

- Also if I am copying it to another table of same structure as:

Insert /*+ append */ into XML_TABLE_2 Select * from XML_TABLE_1.

Then how much space in ROllbackSegment do I need. Is it equal to the size of the table XML_TABLE_1?