How many gigabytes for 5 hours of HD video.

I am about to rent a Nikon D7000 DSLR camera so to shoot a 5-6 hours conferance. My question is how many gigabytes of SD card storage may I need ? I will be recording HD video at 1920x1080 at 24fps. It shoots MOV codec H264. Take up to 2 SD cards.

Thanks in advance.