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

### Instruction:
What is the average Episode Number, when Original Airdate is March 21, 2010, and when Season is less than 3?

### Inputs:
table_name: table, columns: ['Year', 'Show', 'Season', 'Episode', 'Episode number', 'Original airdate']

### Response:
SELECT AVG Episode number FROM table WHERE Original airdate = march 21, 2010 AND Season < 3