supermarket.com is an online marketplace, here is a sample of some of the products available on our site:

Product code	Name	Price
001	Travel Card Holder	£9.25
002	Personalised cufflinks	£45.00
003	Kids T-shirt	£19.95

Our marketing team want to offer promotions as an incentive for our customers to purchase these items.

1. If you spend over £60, then you get 10% off your purchase
2. If you buy 2 or more travel card holders then the price drops to £8.50.

Our check-out can scan items in any order, and because our promotions will change, it needs to be flexible regarding our promotional rules.

The interface to our checkout looks like this (shown in Java):

Checkout co = new Checkout(promotionalRules);
co.scan(item);
co.scan(item);
Double price = co.total();

Implement a checkout system that fulfils these requirements.

Test data

Basket: 001,002,003 Total price expected: £66.78

Basket: 001,003,001 Total price expected: £36.95

Basket: 001,002,001,003 Total price expected: £73.76