CREATE TABLE table_31046 ("City/Municipality" TEXT, "Population  ( 2010 ) " FLOAT, "Area  ( km\\u00b2 ) " TEXT, "Pop. density  ( per km\\u00b2 ) " TEXT, "Income Classification" TEXT)

When 318676 is the population of 2010 and 1st class is the income classification what is the area in kilometers squared?
SELECT "Area (km\u00b2)" FROM table_31046 WHERE "Income Classification" = '1st Class' AND "Population (2010)" = '318676'
SELECT "Area (km\u00b2)" FROM "table_31046" WHERE "Income Classification" = '1st Class' AND "Population (2010)" = '318676'