Well, if you don't need it, might as well get rid of it. Unfortunately, there's an absolute glut of second hand clarinets on the market and I don't think you'd get much for it. Fortunately, the B12 is the most well known beginner's model.
To get the best price, I'd suggest looking at ebay.com and ebay.co.uk for a few days to get an idea of what they sell for online, then advertise it for a bit more locally - in your library, local paper, college etc.
Make sure it's clean, the keys polished, and even get a reed (beginner strength) already set on the MP and check that it plays well.
Or....why not spray it gold and pretend it's a soprano sax?
Steve