How to rewrite this correlated subquery using joins

How to rewrite this correlated subquery using joins . This query is taking more time to execute. i want to reduce the execution time.

SELECT n.*, m.ext_id, m.version, m.cust_id, m.prd_id
FROM ext_pln n, ext_plc_ver m
WHERE m.ext_pln_id = n.ext_pln_id
AND m.plcy_version = (SELECT max(plcy_version) FROM ext_plc_ver WHERE EXTN_CD = m.EXTN_CD)