diff --git a/numpy_questions.py b/numpy_questions.py
index 07a10c1..1734736 100644
--- a/numpy_questions.py
+++ b/numpy_questions.py
@@ -15,11 +15,14 @@
 This will be enforced with `flake8`. You can check that there is no flake8
 errors by calling `flake8` at the root of the repo.
 """
+
+
 import numpy as np
 
 
 def max_index(X):
-    """Return the index of the maximum in a numpy array.
+    """
+    Return the index of the maximum in a numpy array.
 
     Parameters
     ----------
@@ -37,16 +40,25 @@ def max_index(X):
         If the input is not a numpy array or
         if the shape is not 2D.
     """
+    if not isinstance(X, np.ndarray):
+        raise ValueError("The input is not a numpy array")
+    if X.ndim != 2:
+        raise ValueError("The shape is not 2D")
+    """
+    Return the index of the maximum in a numpy array
+    (The row and columnd index of the maximum)
+    """
     i = 0
     j = 0
-
-    # TODO
-
-    return i, j
+    max_index = np.argmax(X)
+    i, j = np.unravel_index(max_index, X.shape)
+    # I convert to int just to avoid show the type(int64) in the output
+    return (int(i), int(j))
 
 
 def wallis_product(n_terms):
-    """Implement the Wallis product to compute an approximation of pi.
+    """
+    Implement the Wallis product to compute an approximation of pi.
 
     See:
     https://en.wikipedia.org/wiki/Wallis_product
@@ -62,6 +74,12 @@ def wallis_product(n_terms):
     pi : float
         The approximation of order `n_terms` of pi using the Wallis product.
     """
-    # XXX : The n_terms is an int that corresponds to the number of
-    # terms in the product. For example 10000.
-    return 0.
+    # So if n_terms = 0 -> product = 1
+    product = 1.0
+    for n in range(1, n_terms + 1):
+        """In wiki the wallis product = the infinite product
+        # representation of π 4*n^2/(4*n^2-1)"""
+        term = (4 * np.square(n)) / (4 * np.square(n) - 1)
+        product *= term
+    pi = 2 * product
+    return pi