Let's go ahead and define all the arguments that are getting passed in. We add lat, lng, and our callback:

var getWeather = (lat, lng, callback) => {

First off let's inject that latitude. We'll take the static latitude, remove it, and between the forward slash and the comma we'll inject it using dollar with our curly braces. This lets us inject a value into our template string; in this case lat. And we can do the exact same thing right after the comma with the longitude. We'll remove the static longitude, use the dollar sign with our curly braces to inject the variable into the string:

var getWeather = (lat, lng, callback) => {
  request({
    url: `https://api.forecast.io/forecast/4a04d1c42fd9d32c97a2c291a32d5e2d/${lat},${lng}`,

Now that the URL is dynamic, the last thing we need to do inside of getWeather is change our console.log calls to callback calls.