Which chemical element has MIN(time-weighted average exposure limit) whose subclass of is group 13 ?
select ?ent where { ?ent wdt:P31 wd:Q11344 . ?ent wdt:P2404 ?obj . ?ent wdt:P279 wd:Q189294. } ORDER BY ASC(?obj)LIMIT 5 
chemical element: Q11344 group 13: Q189294