Number of Happy Customers Ans:

WITH CTE AS (
  SELECT
    customer_id,
    DATE(rental_ts) AS curr_date,
    LEAD(rental_ts, 1) OVER (PARTITION BY customer_id ORDER BY rental_ts) AS next_rental_ts,
    DATE_PART('day', LEAD(rental_ts, 1) OVER (PARTITION BY customer_id ORDER BY rental_ts) -  DATE(rental_ts)) AS days_between_rentals
  FROM rental
  WHERE
    EXTRACT(MONTH FROM rental_ts) = 5
    AND EXTRACT(DAY FROM rental_ts) BETWEEN 24 AND 31 )
	
	
	SELECT
  COUNT(DISTINCT customer_id)
FROM CTE
WHERE days_between_rentals = 1;