diff --git a/Week04/functions_dilara_agac.py b/Week04/functions_dilara_agac.py
new file mode 100644
index 00000000..d47c397a
--- /dev/null
+++ b/Week04/functions_dilara_agac.py
@@ -0,0 +1,38 @@
+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:
+    """
+    Custom equation function.
+
+    :param x: first value
+    :param y: second value
+    :param a: power of x
+    :param b: power of y
+    :param c: divisor
+    :return: result of equation
+    """
+    if not isinstance(x, int) or not isinstance(y, int):
+        raise TypeError("x and y must be integers")
+    if not isinstance(a, int) or not isinstance(b, int) or not isinstance(c, int):
+        raise TypeError("a, b and c must be integers")
+
+    return (x ** a + y ** b) / c
+
+
+def fn_w_counter() -> (int, dict[str, int]):
+    if not hasattr(fn_w_counter, "count"):
+        fn_w_counter.count = 0
+
+    fn_w_counter.count += 1
+
+    caller_name = __name__
+    return fn_w_counter.count, {caller_name: fn_w_counter.count}