A query plan not optimized

CREATE TABLE `c` (

  `cid` int(10) unsigned NOT NULL AUTO_INCREMENT,

  `qid` int(10) unsigned NOT NULL DEFAULT '0',

  `aid` int(10) NOT NULL DEFAULT '0',

  `URN` int(10) NOT NULL DEFAULT '0',

  `in_id` int(10) unsigned NOT NULL DEFAULT '0',

  `out_id` int(10) unsigned NOT NULL DEFAULT '0',

  `DDIstr` varchar(24) NOT NULL,

  `CLIstr` varchar(24) NOT NULL,

  `datetime` datetime NOT NULL DEFAULT '0000-00-00 00:00:00',

  `microtime` varchar(30) NOT NULL DEFAULT '0 0',

  `duration` float NOT NULL DEFAULT '0',

  `wtime` float NOT NULL DEFAULT '0',

  `wrtime` float NOT NULL DEFAULT '0',

  `rtime` float NOT NULL DEFAULT '0',

  `result` varchar(15) DEFAULT NULL,

  `t_cdr` int(10) DEFAULT NULL,

  `c_outcome` int(10) DEFAULT NULL,

  `d_code` varchar(10) DEFAULT NULL,

  `r_cost` float DEFAULT NULL,

  `c_cost` float DEFAULT NULL,

  `dataset` mediumint(8) NOT NULL DEFAULT '0',

  PRIMARY KEY (`cid`),

  KEY `aid` (`aid`),

  KEY `datetime` (`datetime`),

  KEY `result` (`result`),

  KEY `in_id` (`in_id`),

  KEY `out_id` (`out_id`),

  KEY `c_outcome` (`c_outcome`),

  KEY `qid` (`qid`),

  KEY `d_code` (`d_code`),

  KEY `agentid_2` (`aid`,`datetime`),

  KEY `get_max_cid` (`aid`,`cid`),

  KEY `max_cid_2` (`aid`,`result`,`cid`),

  KEY `t_cdr` (`t_cdr`),

  KEY `c_uid` (`URN`,`qid`),

  KEY `DDISTR_2` (`DDISTR`,`datetime`),

  KEY `CLISTR` (`CLISTR`),

  KEY `qid_2` (`qid`,`datetime`)

) ENGINE=InnoDB 

EXPLAIN

SELECT

   c.`cid` AS `cid`

FROM c

WHERE

   c.result IN ('Answered','TPT') AND

   c.`datetime` BETWEEN '2014-05-01 00:00:00' AND '2014-05-29 23:59:59'

   AND c.qid = 42685

ORDER BY cid LIMIT 300;

1       SIMPLE  c       index   qid_2   PRIMARY 4       NULL    1488    Using where

1       SIMPLE  c       range   qid   PRIMARY 12       NULL    1488    Using where