user: Question: serbia has a heat less than 2 and what sum of rank?
Columns: ['Rank', 'Heat', 'Lane', 'Name', 'Nationality', 'Time']
Types: ['real', 'real', 'real', 'text', 'text', 'text']
Sample row: [1.0, 6.0, 4.0, 'Michael Phelps', 'United States', '1:53.70']
SQL:

assistant: SELECT SUM("Rank") FROM "Table" WHERE "Nationality" = 'serbia' AND "Heat" < 2.0;