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

### Instruction:
What is the average rating of viewers 18 to 49 where the total viewer count is 3.93 million and share less than 4?

### Inputs:
table_name: table, columns: ['Episode', 'Air Date', 'Timeslot (EST)', 'Season', 'Rating', 'Share', '18–49', 'Viewers (m)', 'Rank (#)']

### Response:
SELECT AVG 18–49 FROM table WHERE Viewers (m) = 3.93 AND Share < 4