Belоw is а functiоn meаnt tо compute а discount percentage for an order quantity. The specification is: - quantity must be ≥ 1; otherwise throw IllegalArgumentException - 1..5 => 0% - 6..10 => 10% - 11+ => 20% Here is a buggy implementation: public int calculateDiscount(int quantity) { if (quantity >= 5) { return 10; } else if (quantity >= 10) { return 20; } else { return 0; } } Part A (2 pts): Identify the defect(s) in the implementation (briefly). Part B (2 pts): Give ONE concrete test case (input and expected result or exception) that would fail with this implementation and explain in one sentence why it fails. Part C (2 pts): Propose the minimal code change that fixes the defect (show only the corrected lines / small snippet). Part D (2 pts): Explain in one sentence why your fix is correct (mention ordering or boundary logic).