title: Multiplication of 2 variables
body: <p>Supposingly I am working on one of my options in my program.
  I have a text file which has the below content.</p>
  
  <p>The format is <code>Title:Author:Price:QtyAvailable:QtySold</code>, e.g.:</p>
  
  <pre><code>Harry Potter - The Half Blood Prince:J.K Rowling:40.30:10:50
  The little Red Riding Hood:Dan Lin:40.80:20:10
  Harry Potter - The Phoniex:J.K Rowling:50.00:30:20
  Harry Potter - The Deathly Hollow:Dan Lin:55.00:33:790
  Little Prince:The Prince:15.00:188:9
  Lord of The Ring:Johnny Dept:56.80:100:38
  </code></pre>
  
  <p>Below is my function:</p>
  
  <pre><code>printf "%-22s %-16s %-14s %-15s %-13s %s\n", "Title", "Author", "Price","Qty Avail.", "Qty Sold", "Total Sales"
  grep "$1" BookDB.txt | while IFS=: read Title Author Price QtyAvailable QtySold; do
    printf "%-22s %-16s %-14.2f %-15d %-13d %0.2f\n", "$Title" "$Author" "$Price" "$QtyAvailable" "$QtySold"
  done
  </code></pre>
  
  <p>The problem is I need another column which is called Total Sales, computed by multiplying <code>Price</code> and <code>QtySold</code>. However I have tried different ways such as <code>$Price * $QtySold</code> or <code>$3 * $5</code> but still the program does not compute it out for me. Which should be the correct method or way to solve this?</p>