You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: THE 1970s 
Clue: In 1977 Bank of America changed the name of its Bank Americard to this 4-letter word
visa

Category: ISLANDS 
Clue: 3,414-foot-high Carrantuohill west of Killarney is the highest peak on this island
ireland

Category: ESSAYS 
Clue: In addition to his novels, this Russian count wrote religious essays like 1884's "What I Believe"

leo tolstoy