W Mart, a new retail chain, has announced a discount on the total sale amount, in a single transaction, using the following scheme.

Table 1: Discount on Sale Amount

That is, if the total sale amount is $100 then the discount will be $0. However, if the total sale amount is $101 then the discount will be $0.10. If the total sale amount is $500 then the discount will be $40, but if the total sale amount is $501 then the discount will be $40.20.

W Mart keeps track of a customer through a unique customer ID. W Mart gives one reward point for every $100 spent irrespective of the number of transactions. The points accumulate over the time for a customer for his/her purchases. Finally, for each 100 reward points it gives an additional discount of $10 on a purchase over $10 in a transaction.

Write a Python program that, for every transaction, takes input on the customer ID and the total sale amount in the transaction. It then reads a text file called discount.txt that stores information on the discount on sales amount as shown in Table 1 above. The text file stores the information in a plain text format as follows.

Less than $100 --> 0%

From $100 up to less than $500 --> 10%

From $500 up to less than $1,000 --> $40 PLUS 20%

From $1,000 up to less than $2,000 --> $140 PLUS 30%

$2,000 and above --> $440 PLUS 40%

At the end of each transaction, the information related to the transaction would be displayed on the screen. Please see the example as follows.

Customer ID: 1Total sale amount: 110Discount amount: 1Discounted sale amount: 109Reward point: 1Additional discount: 0Additional discounted sale amount: 109Cumulative sale amount for the next reward point: 10Final sale amount: 109Moreover, at the end of each transaction, the information related to the transaction needs to be written (appended) out in a file called sales.txt in the following way:1 110 1 109 1 0 109 10 109However, next time if the same customer spends $50 then the following lines should be displayed on the screen.

Customer ID: 1Total sale amount: 50Discount amount: 0Discounted sale amount: 50Reward point: 1Additional discount: 0Additional discounted sale amount: 50Cumulative sale amount for the next reward point: 60Final sale amount: 50 and 1 50 0 50 1 0 50 60 50 would be written (appended) in the salex.txt file.Again, if the same customer spends $40 then the following lines should be displayed on the screen.Customer ID: 1Total sale amount: 40Discount amount: 0Discounted sale amount: 40Reward point: 2Additional discount: 0Additional discounted sale amount: 40Cumulative sale amount for the next reward point: 0Final sale amount: 40and 1 40 0 40 2 0 40 0 40 would be written (appended) in the salex.txt file.

Use appropriate data structure in writing your code.

All exceptions need to be handled. Invalid inputs need to be handled and asked for a valid input again.

Use functions to make your program well designed, instead of just using a single main function. For example, you could use a function to take inputs from a user, a function to compute the discount, a function to compute the reward points, a function to display the output on the screen and so on. We expect you to use at least four (4) functions other than the main function.

In order to compute the reward points of a customer your program will need to read the sales.txt file. A customer is identified by her/his unique Customer ID, and may appear multiple times in the sales.txt file.

Implement your algorithm in Python.

Avoid duplicate code.

Comment your code as necessary to explain it clearly.

Select 3 sets of test data that will demonstrate the correct "normal" operation of your program.
Run your program using the test data you have selected and save the output it produces in a text file.

Submit:
1. Your algorithm.
2. The table recording your chosen test data.
3. Source code for your Python implementation.
4. Output listings demonstrating the results of using the test data.

It is important that the output listings are not edited in any way