1class Cart
 2  def initialize(items = [])
 3    @items = items
 4  end
 5
 6  def add(product)
 7    @items.push(product)
 8  end
 9
10  def includes?(product)
11    @items.include?(product)
12  end
13
14  def quantity_of(product)
15    @items.find_all do |item|
16      item == product
17    end.count
18  end
19
20  def total_items
21    @items.count
22  end
23
24  def total_price
25    @items.reduce(Money.new(0.00)) do |total, item|
26      total + item.price
27    end
28  end
29end