Exercise 1: Suspending, Resuming and Ending Jobs — Possible Solution
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  $ sleep 600
  ^Z                                  (press Ctrl-Z)
  [1]+  Stopped                 sleep 600

  $ bg
  [1]+ sleep 600 &

  $ sleep 900 &
  [2] 51207

  $ jobs
  [1]-  Running                 sleep 600 &
  [2]+  Running                 sleep 900 &

The current job (+) is job 2, the one most recently started; the
previous job (-) is job 1.

End both using job specs:

  $ kill %1
  $ kill %2          # or: kill %%  (the current job)
  $ jobs
  [1]-  Terminated              sleep 600
  [2]+  Terminated              sleep 900

WHY THIS WORKS AS AN ANSWER
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It goes through the full cycle — foreground, stopped, background,
ended — and shows how the + and - markers follow the most recent
jobs. The PIDs will differ on your system.