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

### Instruction:
When don inglis and ralph smart are the writers how many episode numbers are there?

### Inputs:
table_name: table, columns: ['Episode No.', 'Prod No.', 'Title', 'Directed by', 'Written by', 'Original UK airdate']

### Response:
SELECT COUNT Episode No. FROM table WHERE Written by = Don Inglis and Ralph Smart