user: Question: What is the average sales in billions of walmart, which has more than 15.7 billion in profits?
Columns: ['Rank', 'Company', 'Headquarters', 'Industry', 'Sales (billion $)', 'Profits (billion $)', 'Assets (billion $)', 'Market Value (billion $)']
Types: ['real', 'text', 'text', 'text', 'real', 'real', 'real', 'real']
Sample row: [1.0, 'ExxonMobil', 'USA', 'Oil and gas', 433.5, 41.1, 331.1, 407.4]
SQL:

assistant: SELECT AVG("Sales (billion $)") FROM "Table" WHERE "Company" = 'walmart' AND "Profits (billion $)" > 15.7;