Clairifying this in javascript example 3

this_js_ex3.js

const foo = {
  bar: 10,
  multiplyByBar: function(...args) {
    args.forEach(arg => console.log(arg * this.bar));
  },
};

foo.multiplyByBar(5);        // logs 50
foo.multiplyByBar(5, 10, 15) // logs 50, then 100, then 150

const qux = foo.multiplyByBar;
qux(5)                       // logs NaN (context loss)
qux.call(foo, 5)             // logs 50
qux.call(foo, 5, 10, 15)     // logs 50, then 100, then 150

qux.apply(foo, [5])          // logs 50
qux.apply(foo, [5, 10, 15])  // logs 50, then 100, then 150