title: python - multiply and add each element in list a with list b
body: <p>function:</p>
  
  <p>def unique_common(a, b):</p>
  
  <p>I have two lists, lets say:</p>
  
  <pre><code>a = [2, 3, 5, 7, 9] 
  </code></pre>
  
  <p>and another list </p>
  
  <pre><code>b = [5, 8, 4, 1, 11].
  </code></pre>
  
  <p>This list b gives you the per item price for each item corresponding to the first list a.</p>
  
  <p>For example, if you want to purchase 2 units of the first item, each unit costs $5 per item, to purchase the 3 units of second item it costs $8 per item, and so on.</p>
  
  <p>I want to write a function that calculates the total price for the items in list a. For the example, the result would be </p>
  
  <p>160 = 2*5 + 3*8 + 5*4 + 7*1 + 9*11</p>