Dr. Alexander Graham Bell was buried atop Beinn Bhreagh mountain, on his estate where he had resided increasingly for the last 35 years of his life, overlooking Bras d'Or Lake. He was survived by his wife Mabel, his two daughters, Elsie May and Marian, and nine of his grandchildren.
Over how many years did Bell spend a great deal of time at Beinn Bhreagh?
35