Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_76 (year_opened VARCHAR, students VARCHAR, size VARCHAR)
### Question:
What year was the school opened that has a size of 10 acres and students of na?
### Answer:
SELECT year_opened FROM table_name_76 WHERE students = "na" AND size = "10 acres"