"MacBook Pro (Retina, Late 2013) and Mac Pro (Late 2013) computers can use 4K displays and Ultra HD TVs with OS X or Windows (via Boot Camp)."

http://support.apple.com/kb/HT6008?viewlocale=en_US&locale=e...

(Note that according to that page, the MacBook will only do 30 Hz.)

60 if display port is available (which it is on this Dell).

As Paul mentioned above, Pete was doing the correct thing in contacting our support.

It seems he unfortunately missed one of our replies and therefore considered us unresponsive.