diff --git a/numpy_questions.py b/numpy_questions.py
index 07a10c1..e278976 100644
--- a/numpy_questions.py
+++ b/numpy_questions.py
@@ -40,7 +40,15 @@ def max_index(X):
     i = 0
     j = 0
 
-    # TODO
+    if not isinstance(X, np.ndarray):
+        raise ValueError("Input is not a numpy array")
+
+    if X.ndim != 2:
+        raise ValueError("Input is not 2D")
+
+    max_idx = np.argmax(X)
+
+    i, j = np.unravel_index(max_idx, X.shape)
 
     return i, j
 
@@ -64,4 +72,11 @@ def wallis_product(n_terms):
     """
     # XXX : The n_terms is an int that corresponds to the number of
     # terms in the product. For example 10000.
-    return 0.
+
+    if n_terms == 0:
+        return 2.0
+    n = np.arange(1, n_terms + 1)
+    term = (4 * n**2) / (4 * n**2 - 1)
+    res = 2.0 * np.prod(term)
+
+    return res