Giving one person RLS to another person

Hi,

How about if manager A delegate job to B to monitor team's spend. how can I set the RLS?
for example: line manager A can view L1-L7, line manager A want B to view all expenses exactly same as line manager A. 

currently the RLS setting was:

[Level 1]= UPPER(USERPRINCIPALNAME())
|| [Level 2]= UPPER(USERPRINCIPALNAME())
|| [Level 3]= UPPER(USERPRINCIPALNAME())
|| [Level 4]= UPPER(USERPRINCIPALNAME())
|| [Level 5]= UPPER(USERPRINCIPALNAME())
|| [Level 6]= UPPER(USERPRINCIPALNAME())
|| [Level 7]= UPPER(USERPRINCIPALNAME())
|| [Level 8]= UPPER(USERPRINCIPALNAME())
|| [Level 9]= UPPER(USERPRINCIPALNAME())
|| [Level 10]= UPPER(USERPRINCIPALNAME())
|| [Level 11]= UPPER(USERPRINCIPALNAME())
|| [Level 12]= UPPER(USERPRINCIPALNAME())

so, B only can view himself and his team only ($100) --> Level 1 - level 3 (expenses of team / teams reporting to them)
how can B can view exactly ($1,000) like line manager A --> level 7 (which spend cover level 1-level 7) under A's organisation? 

thanks.
Regards,

Jeane