title: Combining averages of two lists
body: <p>Suppose I have the function:</p>
  
  <pre><code>def avg_grams(l: list) -&gt; float:
      ''' Returns the average grams of parameter list
      '''
      result = 0
      for x in C:
          result += float(x.calories)
      return result / len(l)
  </code></pre>
  
  <p>The function is supposed to return the average grams within a given list of grams. However, if I have two lists, how do I use this function to find the overall average of both lists?</p>
  
  <p>For example: </p>
  
  <pre><code>List A: [2, 3, 4] - Average: 3
  List B: [3, 4, 5] - Average: 4
  Overall avg: 3.5
  </code></pre>