Product code Name  Price FR1 Fruit tea £ 3.11 SR1 Strawberries £ 5.00 CF1 Coffee £11.23 Our CEO is a big fan of buy-one-get-one-free offers and of fruit tea. He wants us to add a rule to do this. The COO, though, likes low prices and wants people buying strawberries to get a price  discount for bulk purchases. If you buy 3 or more strawberries, the price should drop to £4.50. Our check-out can scan items in any order, and because the CEO and COO change  their minds often, it needs to be flexible regarding our pricing rules. The interface to our checkout looks like this (shown in Ruby): co = Checkout.new(pricing_rules) co.scan(item) co.scan(item) Price = co.total Implement a checkout system that fulfils these requirements in Ruby. Test Data Basket: FR1, SR1, FR1, CF1 Total price expected: £22.45 Basket: FR1, FR1 Total price expected: £3.11 Basket: SR1, SR1, FR1, SR1 Total price expected: £16.61