Once Edison had marketed his first successful invention-a stock ticker and printer- for $40,000. I'm confused. Are stock ticker and printer two different machines or just one?
Free · every Monday
Get the Weekly English Kit 📬
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
I just hit upon the idea that it probably a single machine because the word "invention" is used. If they were two machines it would be "inventions". Am I right?