Read the excerpt from "On Becoming an Inventor" by Dean Kamen. Then I heard about a summer job through my uncle who was a dentist. He introduced me to one of his patients who had a business selling audio-visual equipment for big light and music shows. He was looking for some new, better equipment. I spent all summer when I was sixteen building high-powered light-controlled systems that synchronized many Kodak projectors at once, as many as sixty-four to 120 of them, and reduced the cumbersome machines from the size of a refrigerator to the size of a toaster. Not only was this invention used in theaters, but it was sold to the Museum of Natural History and the New York Planetarium to project views of the heavens on the ceiling. To make this new device I had bought every kind of electrical equipment I could find, and still had money left over.

Which detail shows that Kamen's light-controlled systems were very good?

Kamen was introduced to a man who sold audio-visual equipment for big light and music shows.
When he was sixteen, Kamen spent all summer building high-powered light-controlled systems.
One of his inventions was used in theaters, the Museum of Natural History, and the New York Planetarium.
To make one of his devices, he bought every kind of electrical equipment that he could find.