diff --git a/Week04/functions_mustafafurkan_yilmaz.py b/Week04/functions_mustafafurkan_yilmaz.py
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+# 1. custom_power: A lambda function that raises x to the power of e
+custom_power = lambda x=0, /, e=1: x ** e
+
+# 2. custom_equation: Implements (x^a + y^b) / c
+def custom_equation(x: int = 0, y: int = 0, /, a: int = 1, b: int = 1, *, c: int = 1) -> float:
+    """
+    Calculates the equation (x**a + y**b) / c.
+
+    :param x: Base for the first term (positional only)
+    :param y: Base for the second term (positional only)
+    :param a: Exponent for the first term
+    :param b: Exponent for the second term
+    :param c: Divisor (keyword only)
+    :return: The result as a float
+    """
+    # Type checking to satisfy the "must" message requirement in TypeError
+    if not all(isinstance(arg, int) for arg in [x, y, a, b, c]):
+        raise TypeError("All arguments must be integers.")
+
+    return float((x ** a + y ** b) / c)
+
+# 3. fn_w_counter: A stateful function tracking how many times it is called
+# We use a global variable to maintain the state across calls.
+_call_count = 0
+
+def fn_w_counter() -> (int, dict[str, int]):
+    global _call_count
+    _call_count += 1
+    # Returns the current count and a dict mapping the module name to the count
+    return _call_count, {__name__: _call_count}