CREATE TABLE table_62928 ("Campus" CLOB, "Year opened" CLOB, "Students" CLOB, "Size" CLOB, "Location" CLOB)

What year was the school opened that has a size of 10 acres and students of na?
SELECT "Year opened" FROM table_62928 WHERE "Students" = 'na' AND "Size" = '10 acres'
SELECT "Year opened" FROM "table_62928" WHERE "Size" = '10 acres' AND "Students" = 'na'