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

### Instruction:
What is the highest number of not usable satellites when there are more than 0 launch failures, less than 30 retired, and the block is I?

### Inputs:
table_name: table, columns: ['Block', 'Launched', 'Operational', 'Not usable', 'Retired', 'Launch Failures']

### Response:
SELECT MAX Not usable FROM table WHERE Launch Failures > 0 AND Retired < 30 AND Block = block i