Wondering how to connect my early 2015 13 inch MacBook Pro with the Retina Display to my new LG 27UK850-W 4K monitor. I have read several methods but want to know the best one, especially whether it's possibly to just connect them through one HDMI 2.0 cable and get 4K (upscaled) video and normal audio. Cannot test it out since I have just ordered the monitor. Also: say I would watch a 4K video, which would of course be displayed as 2560x1600 by the Retina display. Would the 4K monitor then upscale this from the Mac's output to 4K or would it show the true 4K from the video output?