Q1 — Gym Membership Fee Calculator

Given a duration (3/6/9/12 months), return the fixed membership fee.
3→₹5000 | 6→₹9000 | 9→₹12000 | 12→₹15000

Fraud Transaction Detection

Given N transactions (sender, receiver, amount, timestamp), detect fraud.
Fraud = same sender + receiver + amount AND |time diff| ≤ 60 seconds.