diff --git a/src/my_project/interviews/interview_amazon/round_2/valid_palindrome.py b/src/my_project/interviews/interview_amazon/round_2/valid_palindrome.py
new file mode 100644
index 00000000..f3c4181f
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_2/valid_palindrome.py
@@ -0,0 +1,18 @@
+import re 
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+
+        # to lower case
+        s = s.lower()
+
+        # remove non alpha numeric characters
+        s = re.sub(pattern='[^a-zA-Z0-9]', repl='', string=s)
+
+        len_s = len(s)
+
+        for i in range(len_s//2):
+            if s[i] != s[len_s - 1 -i]:
+                return False 
+            
+        return True
\ No newline at end of file
diff --git a/src/my_project/interviews/top_150_questions_round_17/best_time_to_sell_stock.py b/src/my_project/interviews/top_150_questions_round_17/best_time_to_sell_stock.py
new file mode 100644
index 00000000..0adbeb98
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_17/best_time_to_sell_stock.py
@@ -0,0 +1,19 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+import math 
+
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+
+        min_price = math.inf
+        max_profit = 0
+        len_prices = len(prices)
+
+        for i in range(len_prices):
+
+            if prices[i] < min_price:
+                min_price = prices[i]
+            elif prices[i] - min_price > max_profit:
+                max_profit = prices[i] - min_price
+
+        return max_profit
diff --git a/tests/test_150_questions_round_16/test_best_time_to_sell_stock_round_16.py b/tests/test_150_questions_round_16/test_best_time_to_sell_stock_round_16.py
index ddb38189..60128772 100644
--- a/tests/test_150_questions_round_16/test_best_time_to_sell_stock_round_16.py
+++ b/tests/test_150_questions_round_16/test_best_time_to_sell_stock_round_16.py
@@ -1,3 +1,12 @@
 import unittest
 from src.my_project.interviews.top_150_questions_round_16\
-.best_time_to_sell_stock import Solution
\ No newline at end of file
+.best_time_to_sell_stock import Solution
+
+
+class BestTimeToSellStockTestCase(unittest.TestCase):
+
+    def test_best_time_to_sell_stock(self):
+        solution = Solution()
+        output = solution.maxProfit(prices=[7,1,5,3,6,4])
+        target = 5 
+        self.assertEqual(output, target)
\ No newline at end of file
diff --git a/tests/test_150_questions_round_17/test_best_time_to_sell_stock_round_17.py b/tests/test_150_questions_round_17/test_best_time_to_sell_stock_round_17.py
new file mode 100644
index 00000000..79bbbce0
--- /dev/null
+++ b/tests/test_150_questions_round_17/test_best_time_to_sell_stock_round_17.py
@@ -0,0 +1,12 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_17\
+.best_time_to_sell_stock import Solution
+
+
+class BestTimeToSellStockTestCase(unittest.TestCase):
+
+    def test_best_time_to_sell_stock(self):
+        solution = Solution()
+        output = solution.maxProfit(prices=[7,1,5,3,6,4])
+        target = 5 
+        self.assertEqual(output, target)