user: Question: What is teh average rank of the city of mashhad, which had less than 667770 in 1976?
Columns: ['Rank', 'City', 'Province', 'Date of Official Foundation of Municipality', '2006', '1996', '1986', '1976', '1966', '1956']
Types: ['real', 'text', 'text', 'real', 'real', 'real', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'Tehran', 'Tehran', 1885.0, 7705036.0, 6758845.0, 6042584.0, 4530223.0, 2719730.0, 1512082.0]
SQL:

assistant: SELECT AVG("Rank") FROM "Table" WHERE "City" = 'mashhad' AND "1976" < 667770.0;