You will need to design an application that will receive the customer type and its units of utility used for the billing duration. The application will find out and display the cost per unit based on the customer type and the total charges for that billing cycle. find out the charges using the following data.
Customer Type Units Consumed Cost per unit ($)
Commercial <= 1,000 $0.50 per unit
Commercial 1,000 < $0.50 per unit
Industrial < 800 $0.65 per unit
Industrial 800 <= 2,000 $0.55 per unit
Industrial 2,000 < $0.50 per unit
Residential < 500 $0.85 per unit
Residential 500 <= $0.75 per unit
Make sure that the units consumed entered is a positive number and the Customer Type is valid; otherwise your program should display an error message and ask for the data to be entered again until the user enters valid data. Test your algorithm with the following three sets of data. 
Test case 1: Units used of 799, Customer Type is Industrial 
Test case 2: Units used 500, Customer Type is Residential
Test case 3: Units used 800, Customer Type is Industrial
Test case 4: Units used 1000, Customer Type is Commercial 
Test case 5: Units used 499, Customer Type is Residential