One neat thing about solar and wind energy, that might have national security implications in light of recent events, is that it’s really hard to blockade.

Indeed, and would have earned full marks had he said that, or even showed any awareness that his intermediate results were somehow nonstandard.

I had a student tasked with summing a finite geometric sequence with |r|>1, let’s say 1+2+4+8+16. He had apparently forgotten the formula for that, but knew the formula for the infinite series a/(1-r). Good enough he thinks, and sums 1+2+4+… = -1, then subtracts off the excess terms 32+64+128+… = -32, and gets the correct answer of 31.