user: Question: How many Republican incumbents first elected in 1974?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Status', 'Opponent']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Pennsylvania4', 'Ron Klink', 'Democratic', 1992.0, 'Re-elected', 'Ron Klink (D) 64.2% Ed Peglow (R) 35.8%']
SQL:

assistant: SELECT COUNT("Incumbent") FROM "Table" WHERE "Party" = 'Republican' AND "First elected" = 1974.0;