Write SQL query to solve given problem: List all the cities in Sumatra and state the population of each city.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.Name, T1.Population FROM city AS T1 INNER JOIN locatedOn AS T2 ON T1.Name = T2.City INNER JOIN island AS T3 ON T3.Name = T2.Island WHERE T3.Name = 'Sumatra'