diff --git a/Week04/functions_batuhan_ayyildiz.py b/Week04/functions_batuhan_ayyildiz.py
new file mode 100644
index 00000000..caf59399
--- /dev/null
+++ b/Week04/functions_batuhan_ayyildiz.py
@@ -0,0 +1,20 @@
+
+custom_power = lambda x=0, /, e=1: x ** e
+
+def custom_equation(x: int = 0, y: int = 0, /, a: int = 1, b: int = 1, *, c: int = 1) -> float:
+    return (x ** a + y ** b) / c
+
+def fn_w_counter() -> (int, dict[str, int]):
+    if not hasattr(fn_w_counter, "count"):
+        setattr(fn_w_counter, "count", 0)
+        setattr(fn_w_counter, "caller_dict", {})
+
+    fn_w_counter.count += 1
+    caller = __name__
+
+    if caller not in fn_w_counter.caller_dict:
+        fn_w_counter.caller_dict[caller] = 0
+
+    fn_w_counter.caller_dict[caller] += 1
+
+    return int(fn_w_counter.count), dict(fn_w_counter.caller_dict)