# Measure Customers Ordering from Bottom-Quartile Restaurants Write one PostgreSQL SELECT statement or CTE query. Do not create, alter, or modify tables. ## Schema delivery_orders | column | type | |---|---| | delivery_id | integer | | order_place_time | timestamp | | restaurant_id | integer | | customer_id | integer | order_value | column | type | |---|---| | delivery_id | integer | | order_total | numeric | ## Task For each calendar month in 2021, total sales by restaurant and assign restaurants to four sales buckets with NTILE(4), ordered from lowest monthly sales to highest and then by restaurant ID for deterministic ties. Calculate the percentage of distinct monthly customers who placed at least one order from a restaurant in bucket 1. ## Required Output Return order_month, monthly_customers, bottom_quartile_customers, and bottom_quartile_customer_pct rounded to two decimals. Sort by month ascending. ## Constraints - A customer who orders from several bottom-quartile restaurants counts once. - The denominator is all distinct customers ordering that month. - Use the specified restaurant-ID tie break when assigning buckets. ```hint Separate restaurant and customer grains First compute restaurant-month sales and buckets, then join the bucket membership back to customer orders. ```