diff --git a/Week04/functions_aycaselda_keskin.py b/Week04/functions_aycaselda_keskin.py
new file mode 100644
index 00000000..414a361f
--- /dev/null
+++ b/Week04/functions_aycaselda_keskin.py
@@ -0,0 +1,35 @@
+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:
+    """
+    This function calculates the value of the equation (x**a + y**b) / c.
+
+    :param x: Positional-only base value for the first term.
+    :type x: int
+    :param y: Positional-only base value for the second term.
+    :type y: int
+    :param a: Exponent for 'x'.
+    :type a: int
+    :param b: Exponent for 'y'.
+    :type b: int
+    :param c: Divisor of the equation (keyword-only).
+    :type c: int
+    :return: The result of the custom equation.
+    :rtype: float
+    """
+    return (x**a + y**b) / c
+
+def fn_w_counter() -> (int, dict[str, int]):
+    if not hasattr(fn_w_counter, "call_count"):
+        fn_w_counter.call_count = 0
+        fn_w_counter.callers_dict = {}
+    
+    fn_w_counter.call_count += 1
+    caller_name = __name__
+    
+    if caller_name in fn_w_counter.callers_dict:
+        fn_w_counter.callers_dict[caller_name] += 1
+    else:
+        fn_w_counter.callers_dict[caller_name] = 1
+        
+    return fn_w_counter.call_count, fn_w_counter.callers_dict