Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What year was the school opened that has a size of 10 acres and students of na?

### Inputs:
table_name: table, columns: ['Campus', 'Year opened', 'Students', 'Size', 'Location']

### Response:
SELECT Year opened FROM table WHERE Students = na AND Size = 10 acres