user: Question: Name the sum of rank by average with competition finish more than 8 and average larger than 30
Columns: ['Rank by average', 'Competition finish', 'Couple', 'Total', 'Number of dances', 'Average']
Types: ['real', 'real', 'text', 'real', 'real', 'real']
Sample row: [1.0, 1.0, 'Alesha & Matthew', 584.0, 16.0, 36.5]
SQL:

assistant: SELECT SUM("Rank by average") FROM "Table" WHERE "Competition finish" > 8.0 AND "Average" > 30.0;