user: Question: What is the lowest combined mpg in the US for the a6 transmission, a CO2 g/km under 303, engine capacity over 2461, and L/100km urban (cold) of 15.9?
Columns: ['Manufacturer', 'Transmission', 'Engine Capacity', 'Fuel Type', 'L/100km Urban (Cold)', 'L/100km Extra-Urban', 'L/100km Combined', 'mpg-UK Urban (Cold)', 'mpg-UK Extra-Urban', 'mpg-UK Combined', 'mpg-US Urban', 'mpg-US Extra-Urban', 'mpg-US Combined', 'CO 2 g/km', 'Green Rating']
Types: ['text', 'text', 'real', 'text', 'real', 'real', 'real', 'real', 'real', 'real', 'real', 'real', 'real', 'real', 'text']
Sample row: ['Toyota', 'Multi5', 998.0, 'Petrol', 5.5, 4.1, 4.6, 51.4, 68.9, 61.4, 42.8, 57.4, 51.1, 109.0, 'B']
SQL:

assistant: SELECT MIN("mpg-US Combined") FROM "Table" WHERE "Transmission" = 'a6' AND "CO 2 g/km" < 303.0 AND "Engine Capacity" > 2461.0 AND "L/100km Urban (Cold)" = 15.9;