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

### Instruction:
What is the lowest share with an air date of March 21, 2008 and had viewers larger than 5.15?

### Inputs:
table_name: table, columns: ['Air Date', 'Timeslot', 'Rating', 'Share', '18-49', 'Viewers', 'Weekly Rank']

### Response:
SELECT MIN Share FROM table WHERE Air Date = march 21, 2008 AND Viewers > 5.15