Product code  | Name                   | Price
----------------------------------------------------------
001           | Lavender heart         | £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.

If you spend over £60, then you get 10% of your purchase If you buy 2 or more lavender hearts 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 Ruby):

co = Checkout.new(promotional_rules)
co.scan(item)
co.scan(item)
price = co.total

Implement a checkout system that fulfils these requirements.

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

https://github.com/felixclack/code-tests/blob/master/checkout/README.md