I'm not sure if ill explain this right, but in the previous video on the Group 4 words, he said you can choose either concept. Once you have chosen a concept, you negate it, then make it the necessary condition. Then you take the contrapositive as the last step.

The answer for #5 shows both circumstances in whether you chose "applied to producing power at traditional plants" or "recent tech advance producing" as your necessary condition. The answers are just contrapositives of one another. So if you wanted to chose "recent tech advance producing" as your necessary condition, you could do that

For me i chose Recent tech adv. producing elec. power (RTA PEP) as my necessary condition & Applied to Producing Power (App. to PP) as my sufficient.

So i wrote it out at first as:

App. to PP > /RTA PEP

-then took the contrapositive and my final answer was

RTA PEP > /App. to PP

i tried but unfortunately i was not able to download, maybe try screenshotting?