user: Question: What were the investment earnings in a year when total revenue was $21,779,618?
Columns: ['Year', 'Property Taxes', 'Investment Earnings', 'Other Local Sources', 'State & Federal', 'Total Revenue']
Types: ['real', 'text', 'text', 'text', 'text', 'text']
Sample row: [2005.0, '$24,384,901', '$255,041', '$2,670,060', '$13,581,968', '$40,891,700']
SQL:

assistant: SELECT "Investment Earnings" FROM "Table" WHERE "Total Revenue" = '21,779,618';