title: total number of comparisons required to merge sorted files
body: <p>Given 4 sorted files containing 15,3,9 and 8 records what is the total number of comparisons required to merge them into a single sorted file?</p>
  
  <p>Assume that we are using the merge step (from merge sort) for this.</p>
  
  <p>I know that the merge step takes O(N) time to execute. But how many comparisons does it make?</p>