Any suggestions on tuning below query.

SELECT A.AMT_MATURITY
  FROM AMT_HISTORY A
 WHERE A.ACCT_NO = 100252652    
   AND A.DEP_NO = 5
   AND A.DAT_CALC = (SELECT MAX(DAT_CALC)
                       FROM AMT_HISTORY
                      WHERE COD_ACCT_NO = A.ACCT_NO
                        AND COD_DEP_NO = A.DEP_NO);

Explain plan:

SELECT STATEMENT, GOAL = ALL_ROWS			10	1	100
 FILTER					
  SORT GROUP BY			10	1	100
   HASH JOIN			5	1	100
    TABLE ACCESS FULL	HOST1	AMT_HISTORY	2	1	60
    TABLE ACCESS FULL	HOST1	AMT_HISTORY	2	2	80

CREATE INDEX ... ON AMT_HISTORY ( ACCT_NO, DEP_NO, DAT_CALC ) COMPUTE STATISTICS ...