basket.ts

export class Basket {
  //...
  
  private applyDiscount(totalOfSameBookBorrowed: number, price: number): number {
      switch (totalOfSameBookBorrowed) {
          case 1:
              return price
          case 2:
              return price * (1 - 0.05)
          default:
              return price * (1 - 0.25)
      }
  }
}