title: Why is BigNumber with etherjs returning 0
body: <p>I am using <a href="https://docs.ethers.io/v5/api/utils/bignumber/" rel="nofollow noreferrer"><code>BigNumber</code></a> from etherjs and I am doing this very simple operation:</p>
  <pre><code>const cost = BigNumber.from(3)
      .div(BigNumber.from(1000))
      .mul(BigNumber.from(3));
  
    console.log(cost.toString());
  </code></pre>
  <p>It outputs '0', but should be 0.09.</p>
  <p>Why? What am I doing wrong?</p>