NSString memory management question

FROM : Rick Mann
DATE : Wed Apr 23 00:25:35 2008

I wrote a routine that creates a CFStringRef from some USB calls. I 
use it like this:

   NSString* s = (NSString*) createStringDescriptor(dev, stringIndex);
   [mSerialNumberDisplay setStringValue: [s lowercaseString]];
   [s release];


Two main questions: am I right to release the bridged NSString* s? 
and, what happens in -lowercaseString? How does that get released?

TIA,
--
Rick