Checkout Kata

1. Implement the code for a checkout system that handles pricing schemes such as "pineapples cost 50, three pineapples cost 130."
2. Implement the code for a supermarket checkout that calculates the total price of a number of items. In a normal supermarket, things are identified using Stock Keeping Units, or SKUs. In our store, we’ll use individual letters of the alphabet (A, B, C, and so on). Our goods are priced individually. In addition, some items are multi-priced: buy n of them, and they’ll cost you y pence. For example, item A might cost 50 individually, but this week we have a special offer: buy three As and they’ll cost you 130. In fact the prices are:

SKU	Unit Price	Special Price
A	50	3 for 130
B	30	2 for 45
C	20
D	15

The checkout accepts items in any order, so that if we scan a B, an A, and another B, we’ll recognize the two Bs and price them at 45 (for a total price so far of 95). The pricing changes frequently, so pricing should be independent of the checkout.

The interface to the checkout could look like:

interface ICheckout
{
    void Scan(string item);
    int GetTotalPrice();
}

Be sure to commit to version control frequently.

Your code should adhere to SOLID principles:

• Single responsibility principle
• Open/closed principle
• Liskov substitution principle
• Interface segregation principle
• Dependency inversion principle