how do you shedule a job using dbms_job to run every Sat at 3:00AM ???

let sat if I have this package below:

var j number
begin
dbms_job.submit
(
:j,
'SYS.DBMS_UTILITY.ANALYZE_SCHEMA(''CONTRACKER'',''COMPUTE'');',
sysdate,'sysdate+(90/(24*60*60))'
);
COMMIT;
end;
/

The above job run very 90 sec but now I have it to run every sat at 3:00am

thanks