Minor tweak to exercise 1.9

Author: dabeaz

Notes/01_Introduction/03_Numbers.md

@@ -213,14 +213,14 @@ Modify the program so that extra payment information can be more generally handl
 Make it so that the user can set these variables:
 
 ```python
-extra_payment_start_month = 60
+extra_payment_start_month = 61
 extra_payment_end_month = 108
 extra_payment = 1000
 ```
 
 Make the program look at these variables and calculate the total paid appropriately.
 
-How much will Dave pay if he pays an extra $1000/month for 4 years starting in year 5 of the mortgage?
+How much will Dave pay if he pays an extra $1000/month for 4 years starting in year 5 of the mortgage?  
 
 ### Exercise 1.10: Making a table
 

Solutions/1_10/mortgage.py

@@ -7,15 +7,15 @@
 month = 0
 
 extra_payment = 1000.0
-extra_payment_start_month = 60
+extra_payment_start_month = 61
 extra_payment_end_month = 108
 
 while principal > 0:
     month = month + 1
     principal = principal * (1+rate/12) - payment
     total_paid = total_paid + payment
 
-    if month > extra_payment_start_month and month <= extra_payment_end_month:
+    if month >= extra_payment_start_month and month <= extra_payment_end_month:
         principal = principal - extra_payment
         total_paid = total_paid + extra_payment