rule set for html notfication

Hello,

Please i have rule set to send emails to specific group. lets say that change was opened by user A and change owner is the same user A, i want only one email to be send to that user as he is in both groups. i tried to put into RAD expression

requested.by in $L.file=contact() or not  (same(coordinator in $L.file, change.owner in $L.file))

which still send more than one email and

not  (null(requested.by in $L.file)) or not  (same(coordinator in $L.file, change.owner in $L.file))

but both of these still send more than one mail. i tried to switch  "or" with "and" but without luck

 

thank you for help