diff --git a/Week04/functions_gulsum_ceylan.py b/Week04/functions_gulsum_ceylan.py
new file mode 100644
index 00000000..00d76d95
--- /dev/null
+++ b/Week04/functions_gulsum_ceylan.py
@@ -0,0 +1,41 @@
+
+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:
+    """
+    Calculate a mathematical equation.
+
+    :param x: First integer.
+    :param y: Second integer.
+    :param a: Exponent for x.
+    :param b: Exponent for y.
+    :param c: Divisor.
+    :return: Calculated result.
+    """
+    return (x ** a + y ** b) / c
+
+
+total_calls = 0
+calls_by_module = {}
+
+
+def fn_w_counter() -> (int, dict[str, int]):
+    global total_calls
+
+    total_calls += 1
+    module_name = __name__
+
+    calls_by_module[module_name] = (
+        calls_by_module.get(module_name, 0) + 1
+    )
+
+    return total_calls, calls_by_module.copy()