diff --git a/calculator.py b/calculator.py
index a46affd..674b26e 100644
--- a/calculator.py
+++ b/calculator.py
@@ -40,45 +40,88 @@
 
 
 """
-
+import traceback
+
+def index(*args):
+    """ Returns a howto for the calculator application"""
+    howto = """
+      <h1>How To Use WSGI Calculator</h1>
+      <h2>Examples</h2>
+      To add integers: <a href="/add/23/42">http://localhost:8080/add/23/42</a><br>
+      To subtract integers: <a href="/subtract/23/42">http://localhost:8080/subtract/23/42</a><br>
+      To multiply: <a href="/multiply/3/5">http://localhost:8080/multiply/3/5</a><br>
+      To divide: <a href="/divide/22/11">http://localhost:8080/divide/22/11</a><br>
+      """
+    return howto
 
 def add(*args):
     """ Returns a STRING with the sum of the arguments """
+    args = [int(i) for i in args]
+    return str(sum(args))
+
+def subtract(*args):
+    """ Returns a STRING with the subtraction of the arguments """
+    diff = int(args[0]) - int(args[1])
+    return str(diff)
 
-    # TODO: Fill sum with the correct value, based on the
-    # args provided.
-    sum = "0"
+def multiply(*args):
+    """ Returns a STRING with the product of the arguments """
+    product = int(args[0]) * int(args[1])
+    return str(product)
 
-    return sum
+def divide(*args):
+    """ Returns a STRING with the division of the arguments """
+    quotient = int(args[0]) / int(args[1])
+    return str(int(quotient))
 
-# TODO: Add functions for handling more arithmetic operations.
 
 def resolve_path(path):
     """
     Should return two values: a callable and an iterable of
     arguments.
     """
-
-    # TODO: Provide correct values for func and args. The
-    # examples provide the correct *syntax*, but you should
-    # determine the actual values of func and args using the
-    # path.
-    func = add
-    args = ['25', '32']
-
+    funcs = {
+      '': index,
+      'add':add,
+      'subtract':subtract,
+      'multiply':multiply,
+      'divide':divide,
+    }
+    path = path.strip('/').split('/')
+    func_name = path[0]
+    args = path[1:]
+    try:
+      func = funcs[func_name]
+    except KeyError:
+      raise NameError
     return func, args
 
 def application(environ, start_response):
-    # TODO: Your application code from the book database
-    # work here as well! Remember that your application must
-    # invoke start_response(status, headers) and also return
-    # the body of the response in BYTE encoding.
-    #
-    # TODO (bonus): Add error handling for a user attempting
-    # to divide by zero.
-    pass
+    headers = [('Content-type', 'text/html')]
+    try:
+      path = environ.get('PATH_INFO', None)
+      if path is None:
+        raise NameError
+      func, args = resolve_path(path)
+      body = func(*args)
+      status = "200 OK"
+    except NameError:
+      status = "404 Not Found"
+      body = "404 Not Found"
+    except ZeroDivisionError:
+      status = "400 Bad Request"
+      body = "400 Bad Request: Division by Zero"
+    except Exception:
+      status = "500 Internal Server Error"
+      body = "500 Internal Server Error"
+      print(traceback.format_exc())
+    finally:
+      headers.append(('Content-length', str(len(body))))
+      start_response(status, headers)
+    return [body.encode('utf8')]
+
 
 if __name__ == '__main__':
-    # TODO: Insert the same boilerplate wsgiref simple
-    # server creation that you used in the book database.
-    pass
+    from wsgiref.simple_server import make_server
+    srv = make_server('localhost', 8080, application)
+    srv.serve_forever()