package.js

class Box {
  constructor() {
    this.price = 50;
    this.products = [];
  }
  
  get totalPrice() {
    const productsTotalPrice = this.products.reduce(
      (totalPrice, product) => totalPrice + product.price, 0
    );
    return productsTotalPrice + this.price;
  }
  
  addProduct(product) {
    this.products.push(product);
  }
}

class Product {
  constructor(name, price) {
    this.name = name;
    this.price = price;
  }
}

const pen = new Product('pen', 60);
const eraser = new Product('eraser', 20);
const box = new Box();

box.addProduct(pen);
box.addProduct(pen);
box.addProduct(pen);
box.addProduct(eraser);

box.totalPrice; // 250