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

### Instruction:
What is the series number that has a production code of 50021–50025?

### Inputs:
table_name: table, columns: ['Number in series', 'Number in season', 'Title', 'Directed by', 'Original air date', 'Production code']

### Response:
SELECT MAX Number in series FROM table WHERE Production code = 50021–50025