diff --git a/Week04/functions_elifsude_yilmaz.py b/Week04/functions_elifsude_yilmaz.py
new file mode 100644
index 00000000..8faaa7c0
--- /dev/null
+++ b/Week04/functions_elifsude_yilmaz.py
@@ -0,0 +1,45 @@
+import inspect
+
+
+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:
+    """
+    :param x: first integer value
+    :param y: second integer value
+    :param a: coefficient for x
+    :param b: coefficient for y
+    :param c: divisor
+    :return: result of the equation
+    """
+  
+    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_total_counter = 0
+_fn_callers: dict[str, int] = {}
+
+
+def fn_w_counter() -> (int, dict[str, int]):
+    global _fn_total_counter, _fn_callers
+
+    _fn_total_counter += 1
+
+    caller_module = inspect.stack()[1].frame.f_globals.get("__name__", "__main__")
+
+    _fn_callers[caller_module] = _fn_callers.get(caller_module, 0) + 1
+
+    return _fn_total_counter, {caller_module: _fn_callers[caller_module]}