How to check when the RMAN backup will complete

Query:
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col TARGET for a25
set lines 300
col OPNAME for a50
SELECT target,OPNAME,sum(sofar), sum(totalwork),sum(sofar)*100/sum(totalwork) Percntg,sum(ELAPSED_SECONDS/60) ETIME,max(time_remaining/60) RTIME
FROM v$session_longops WHERE time_remaining > 0 and sofar!=totalwork and OPNAME like '%RMAN%' group by target,OPNAME;