HI, I have a 2015 Macbook Pro 13" Retina, and a LG 27UD88 4k monitor. I tried to connect the laptop to the monitor using 2 methods: 1. HDMI to HDMI cable, and the max I was able to get 4k @ 30hz 2. Mini Display to HDMI cable, and the max I was able to get 1080p @ 60hz I know the laptop is capable of doing 4K @ 60hz. What am I doing wrong?