Segment customers into 4 tiers based on their total account balance using NTILE. Tier 1 is the top 25%% by balance, tier 4 is the bottom 25%%. Return first_name, last_name, total_balance, tier, and the count of customers in each tier (tier_size). Use a CTE for the tier assignment and a window function for tier_size. Order by tier ascending, total_balance descending.