diff --git a/Week04/decorators_esra_sepik.py b/Week04/decorators_esra_sepik.py
new file mode 100644
index 00000000..bc34edf3
--- /dev/null
+++ b/Week04/decorators_esra_sepik.py
@@ -0,0 +1,31 @@
+import time
+import tracemalloc
+
+
+def performance(fn):
+    """
+    Decorator that measures the execution time and memory usage of a function.
+    Statistics are kept in performance.counter, performance.total_time
+    and performance.total_mem.
+    """
+    def _inner(*args, **kwargs):
+        tracemalloc.start()
+        begin = time.time()
+        output = fn(*args, **kwargs)
+        end = time.time()
+        used = tracemalloc.get_traced_memory()[1]
+        tracemalloc.stop()
+
+        setattr(performance, "counter", getattr(performance, "counter", 0) + 1)
+        setattr(performance, "total_time", getattr(performance, "total_time", 0) + (end - begin))
+        setattr(performance, "total_mem", getattr(performance, "total_mem", 0) + used)
+        return output
+
+    _inner.__name__ = fn.__name__
+    _inner.__doc__ = fn.__doc__
+    return _inner
+
+
+performance.counter = 0
+performance.total_time = 0
+performance.total_mem = 0
diff --git a/Week04/functions_esra_sepik.py b/Week04/functions_esra_sepik.py
new file mode 100644
index 00000000..18dc055b
--- /dev/null
+++ b/Week04/functions_esra_sepik.py
@@ -0,0 +1,36 @@
+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:
+    """
+    Calculates an equation using the given integers.
+
+    The formula is ``(x ** a + y ** b) / c``.
+
+    :param x: positional-only value, defaults to 0
+    :type x: int
+    :param y: positional-only value, defaults to 0
+    :type y: int
+    :param a: exponent for x, defaults to 1
+    :type a: int
+    :param b: exponent for y, defaults to 1
+    :type b: int
+    :param c: keyword-only divisor, defaults to 1
+    :type c: int
+    :returns: the result of the equation
+    :rtype: float
+    """
+    numerator = pow(x, a) + pow(y, b)
+    return numerator / c
+
+
+_call_count = 0
+_caller_counts: dict[str, int] = {}
+
+
+def fn_w_counter() -> (int, dict[str, int]):
+    global _call_count
+    caller_name = globals()["__name__"]
+    _call_count += 1
+    _caller_counts[caller_name] = _caller_counts.setdefault(caller_name, 0) + 1
+    return (_call_count, dict(_caller_counts))