further revision

brick2.rb

class Order < ActiveRecord::Base
  #...  
  scope :high_margin, where('price_to_manufacture * 10 <= profit')
  scope :with_profit_of_at_least, lambda{|account| where('profit >= ?', amount) }
 
end
 
class Customer < ActiveRecord::Base
 
  has_many :orders
  scope :big_spenders, joins(:orders).merge(Order.high_margin.with_profit_of_at_least(25000))
  
end