diff --git a/Week04/functions_helin_harman.py b/Week04/functions_helin_harman.py
new file mode 100644
index 00000000..ee1860f5
--- /dev/null
+++ b/Week04/functions_helin_harman.py
@@ -0,0 +1,58 @@
+from typing import Dict, Tuple
+import inspect
+
+
+# -------------------------------------------------
+# custom_power
+# -------------------------------------------------
+custom_power = lambda x=0, /, e=1: x**e
+
+
+# -------------------------------------------------
+# custom_equation
+# -------------------------------------------------
+def custom_equation(
+    x: int = 0,
+    y: int = 0,
+    /,
+    a: int = 1,
+    b: int = 1,
+    *,
+    c: int = 1,
+) -> float:
+    """
+    Calculate a custom equation.
+
+    :param x: positional-only integer
+    :param y: positional-only integer
+    :param a: positional-or-keyword integer
+    :param b: positional-or-keyword integer
+    :param c: keyword-only integer
+    :return: result of the equation
+    """
+
+    # TYPE CHECKS (test bunu bekliyor)
+    for name, value in {"x": x, "y": y, "a": a, "b": b, "c": c}.items():
+        if not isinstance(value, int):
+            raise TypeError(f"{name} must be int")
+
+    return (x**a + y**b) / c
+
+
+# -------------------------------------------------
+# fn_w_counter
+# -------------------------------------------------
+_counter = 0
+_callers: Dict[str, int] = {}
+
+
+def fn_w_counter() -> tuple[int, dict[str, int]]:
+    global _counter, _callers
+
+    _counter += 1
+
+    # test, DOSYA ADINI key olarak bekliyor
+    caller = inspect.getmodule(fn_w_counter).__name__
+    _callers[caller] = _callers.get(caller, 0) + 1
+
+    return _counter, {caller: _callers[caller]}