public static void RunObserver() { IInvestor steve = new Investor(100, "Steve Jobs"); IInvestor bill = new Investor(101, "Bill Gates"); IInvestor james = new Investor(102, "James Gosling"); IStock philipsStock = new Stock("Apple Inc.", 1000.0); philipsStock.Register(steve); philipsStock.Register(bill); IStock aluStock = new Stock("Microsoft Corp.", 500.0); aluStock.Register(steve); aluStock.Register(james); philipsStock.Price += 2.0; aluStock.Price += 3.5; philipsStock.Price -= 0.7; aluStock.Price -= 1.4; }