nswer to the previous part, you had
      to replace $r$ and $h$ with what they equaled in terms of
      $t$. What part of the notation $\dfrac{dV}{dt}=DV(g(t))\,
      Dg(t)$ tells you to replace $r$ and $h$ with what they equal
      in terms of $t$?</li>
    </ol>
  </div>Let's look at some physical examples involving motion and
  temperature, and try to connect what we know should happen to
  what the chain rule states.

  <div class="problem" id="horse-track-chain-rule-introduction">
    Consider
    