Need help with a problem using discounts to figure a final price.

[airic1992]

The local t-shirt shop sells shirts that retail for $12. Quantity dis-
counts are given as follow:

Number of Shirts Discount
5–10 10%
11–20 15%
21–30 20%
31 or more 25%
Write a program that prompts the user for the number of shirts required
and then computes the total price. Make sure the program accepts only
nonnegative input.

[vasilenko93]

This code uses a bunch of if and else ifs to set the new price of the shirt.

const double PRICE = 12.00;
double newPrice = 0;

int amount ;

cout << "How much shirts do you want? "
cin >> amount ;

if(amount >= 5 && amount <= 10)
    newPrice = PRICE - (PRICE * 0.1)
else if(amount >= 11 && amount <= 20)
    newPrice = PRICE - (PRICE * 0.15)
else if(amount >= 21 && amount <= 30)
    newPrice = PRICE - (PRICE * 0.2)
else if(amount >= 31)
    newPrice = PRICE - (PRICE * 0.25)
else
    newPrice = PRICE;

cout << "Buying " << amount << " shirt(s) gives you a price of  "
        << newPrice << " per shirt." << endl;
cout << "Instead of the original " << PRICE << " per shirt."

How much shirts do you want? 15
Buying 15 shirt(s) gives you a price of 10.2 per shit.
Instead of the original 12 per shirt.