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

### Instruction:
What is the sum of the numbers in series written by sam meikle, which have 21 numbers in the season?

### Inputs:
table_name: table, columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Ratings']

### Response:
SELECT SUM No. in series FROM table WHERE Written by = sam meikle AND No. in season = 21