Hyphenated names of attributes in JavaScript

Custom attributes can contain hyphens in their names, like this:

html<div id="elem" data-my-test="1000"></div>

To refer to such attributes, use camelCase:

javascriptlet elem = document.querySelector('#elem');
console.log(elem.dataset.myTest);

Задание 1

Given the following code:

html<div id="elem" data-product-price="1000" data-product-amount="5">
  apples
</div>

Make it so that when you click on the div, the purchase price is added to the end of its text, equal to the price multiplied by the quantity.