Inside the hidden hotels that keep Mount Everest running

The Everest base-camp trek takes days and over 100 kilometers of hiking. Along the journey, teahouses provide a hot meal and a warm bed. But the porters, who carry upwards of 45 kilograms each day, usually stay in separate lodging from the climbers who hire them. And at over 4,200 meters, getting anything to a teahouse, whether on back or by yak, is a logistical nightmare. So, what's it like inside these teahouses? And how do you run a business at the top of the world?