The Seven Summits are the highest mountains of each of the world’s seven continents. Richard Bass compiled this list in the 1980s and established as a mountaineering challenge the summiting of all seven. Reinhold Messner, another climber, proposed substituting one of the mountains with New Guinea’s Carstensz Pyramid (4,884 m). From a mountaineering standpoint, Messner’s list is considered the more challenging one. As of March 2007, how many climbers had scaled all of the peaks on both lists? Discuss