title: How can i calculate for the estimated completion time of both process
body: <p>A certain computer system runs in a multi-programming environment using a non-preemptive
  algorithm. In this system, two processes A and B are stored in the process queue,
  and A has a higher priority than B. The table below shows estimated execution time for each
  process; for example, process A uses CPU, I/O, and then CPU sequentially for 30, 60, and 30
  milliseconds respectively. Which of the following is the estimated time in milliseconds
  to complete both A and B? Here, the multi-processing overhead of OS is negligibly
  small. In addition, both CPU and I/O operations can be executed concurrently, but I/O
  operations for A and B cannot be performed in parallel.</p>
  
  <p>UNIT : millisecond</p>
  
  <pre><code>                 CPU                    I/O                  CPU
  </code></pre>
  
  <p>A_______________30___________________60_________________30</p>
  
  <p>B_______________45___________________45__________________-- </p>
  
  <p>Please help me.. i need to explain this in front of the class tomorrow but i cant seem get the idea of it... </p>