Given these services, what will OrderService.getOrderDetails() return?

Given these services, what will OrderService.getOrderDetails() return?

import { Injectable } from '@angular/core';
@Injectable({ providedIn: 'root' })
export class ProductService {
  getProduct() { return 'Book'; }
}
@Injectable({ providedIn: 'root' })
export class OrderService {
  constructor(private productService: ProductService) {}
  getOrderDetails() {
    return `Order includes: ${this.productService.getProduct()}`;
  }
}