Complete Orders Analysis

Merge orders with customers and find the total spending per customer for completed orders only. Sort by total spending descending.

Available Data:

• orders: order_id, customer_id, amount, status
• customers: customer_id, name, city

Requirements:

• Filter orders to only 'completed' status
• Merge with customers to get names
• Group by customer name and sum the amount
• Sort by total amount descending
• Result should be a Series with customer name as index