I think you’d need roughly a billion of them. Minus the 20 you have, of course.

They didn’t ask if it would be easy.

They didn’t ask if it it could be done without spending billions, or whether it would be feasible, i.e., practical, just whether it would be possible.

Do you mean one computer from 1985? No. There is no computer from that year that had enough RAM. If you mean all the computers from 1985, working together, then yes. You only need sufficient RAM, a Turing-complete machine, and probably some centuries to do it.

It’s true that there are alternatives, like a used mini-PC, or an Orange Pi. On the other hand, you can just wait a bit. It’s not the same situation with the Pi 4 being perpetually out of stock for years. That was because of ongoing chip shortages during the pandemic, and the subsequent backlog, which is no longer an issue. This is just because it’s a new product, so there are a ton of pre-orders. Some of those are scalpers who are thinking that the availability will remain low, and sustain stupid prices, but I think they’ll be disappointed. Once the initial rush is cleared out, it should be fine.