diff --git a/q4/q4_3b/movies.json b/q4/q4_3b/movies.json
new file mode 100644
index 0000000..32b16f9
--- /dev/null
+++ b/q4/q4_3b/movies.json
@@ -0,0 +1,105 @@
+{
+    "data_code": "B-20260705-9162",
+    "movies": [
+        {
+            "id": 1,
+            "title": "放牛班的春天",
+            "director": "Frank Darabont",
+            "year": 2007,
+            "rating": 8.9,
+            "duration": 155,
+            "genre": "悬疑",
+            "actors_count": 5
+        },
+        {
+            "id": 2,
+            "title": "霸王别姬",
+            "director": "陈凯歌",
+            "year": 2018,
+            "rating": 6.6,
+            "duration": 143,
+            "genre": "剧情",
+            "actors_count": 4
+        },
+        {
+            "id": 3,
+            "title": "星际穿越",
+            "director": "Robert Zemeckis",
+            "year": 2018,
+            "rating": 8.4,
+            "duration": 165,
+            "genre": "悬疑",
+            "actors_count": 5
+        },
+        {
+            "id": 4,
+            "title": "肖申克的救赎",
+            "director": "James Cameron",
+            "year": 2008,
+            "rating": 8.6,
+            "duration": 124,
+            "genre": "剧情",
+            "actors_count": 5
+        },
+        {
+            "id": 5,
+            "title": "盗梦空间",
+            "director": "宫崎骏",
+            "year": 1993,
+            "rating": 7.8,
+            "duration": 90,
+            "genre": "爱情",
+            "actors_count": 2
+        },
+        {
+            "id": 6,
+            "title": "泰坦尼克号",
+            "director": "Christopher Nolan",
+            "year": 2001,
+            "rating": 6.7,
+            "duration": 175,
+            "genre": "喜剧",
+            "actors_count": 4
+        },
+        {
+            "id": 7,
+            "title": "忠犬八公的故事",
+            "director": "Lasse Hallström",
+            "year": 2004,
+            "rating": 8.2,
+            "duration": 91,
+            "genre": "动画",
+            "actors_count": 3
+        },
+        {
+            "id": 8,
+            "title": "三傻大闹宝莱坞",
+            "director": "Rajkumar Hirani",
+            "year": 2011,
+            "rating": 6.3,
+            "duration": 175,
+            "genre": "冒险",
+            "actors_count": 3
+        },
+        {
+            "id": 9,
+            "title": "阿甘正传",
+            "director": "Christophe Barratier",
+            "year": 2022,
+            "rating": 7.9,
+            "duration": 107,
+            "genre": "动画",
+            "actors_count": 4
+        },
+        {
+            "id": 10,
+            "title": "千与千寻",
+            "director": "Christopher Nolan",
+            "year": 1993,
+            "rating": 7.2,
+            "duration": 129,
+            "genre": "悬疑",
+            "actors_count": 3
+        }
+    ]
+}
diff --git a/q4/q4_3b/q4_3b.py b/q4/q4_3b/q4_3b.py
new file mode 100644
index 0000000..124902a
--- /dev/null
+++ b/q4/q4_3b/q4_3b.py
@@ -0,0 +1,21 @@
+# q4_3b.py
+import json
+import matplotlib.pyplot as plt
+
+with open("../q4_2/movies.json", "r", encoding="utf-8") as f:
+    data = json.load(f)
+
+movies = data["movies"]
+
+durations = []
+for m in movies:
+    durations.append(m["duration"])
+
+plt.hist(durations, bins=5, color="green")
+plt.title("时长分布")
+plt.xlabel("时长（分钟）")
+
+plt.savefig("q4_3b_hist.png", dpi=150)
+plt.close()
+
+print("✅ 时长直方图生成成功！")
\ No newline at end of file
diff --git a/q4/q4_3b/q4_3b_hist.png b/q4/q4_3b/q4_3b_hist.png
new file mode 100644
index 0000000..2db26b9
Binary files /dev/null and b/q4/q4_3b/q4_3b_hist.png differ