text: const Mall = require('./Mall');
  const Shopper = require('./Shopper');
  const Store = require('./Store');
  
  let yusuf = new Shopper("Yusuf");
  let ugur = new Shopper("Ugur");
  let berk = new Shopper("Berk");
  
  let piazzaAVM = new Mall();
  
  let nike = new Store("Nike");
  let adidas = new Store("Adidas");
  
  nike.subscribe(yusuf);
  nike.subscribe(ugur);
  nike.subscribe(berk);
  nike.subscribe(piazzaAVM);
  
  adidas.subscribe(yusuf);
  adidas.subscribe(piazzaAVM);
  
  nike.sale(50);
  adidas.sale(20);
  
  