title: simple process rollback question
body: <p>while revising for an exam, i came across this simple question asking about rollbacks in processes. i understand how rollbacks occur, but i need some validation on my answer.
  The question:</p>
  
  <p><img src="https://i.stack.imgur.com/iVatR.jpg" alt="alt text">
  <img src="https://i.stack.imgur.com/UB49c.jpg" alt="alt text"></p>
  
  <p>my confusion results from the fact that there is interprocess communication between the processes. does that change anything in terms of where to rollback? my answer would be R13, R23, R32 and R43. any help is greatly appreciated! thanks!</p>