question:  How did Ninian, Raymond, and the other cousins go back in time?
context: No one, least of all Martin, could dispute that a man's life should be guarded by his kin—but by those who hadn't been born yet? Nobody in the neighborhood was surprised when Martin's mother disappeared and Ninian came to take care of him. Besides, if she really was his great-great-grand-daughter, as she said, why would she tell him to call her " Aunt Ninian "? Martin was told to call him Uncle Raymond. From time to time, there were other visitors—Uncles Ives and Bartholomew and Olaf, Aunts Ottillie and Grania and Lalage, and many more—all cousins to one another, he was told, all descendants of his. The non-glass part of the house was of neat, natural-toned wood, with a neat green lawn in front and a neat parti-colored garden in back. It was then that Martin began to realize that either the whole lot of them were insane, or what Ninian had told him at first was the truth. When Martin was sixteen, Raymond took him aside for the talk Ninian had promised five years before. "We just come a couple of centuries or so later, that's all. We're virtually the same people ... although it is amazing what a difference two hundred odd years of progress and polish can make in a species, isn't it?" All that sort of thing comes from the out-system planets. And, on those worlds, it's far cheaper to use native labor than to ship out all that expensive machinery. But he wasn't, for by now he had little respect left for any of his descendants. Unaware of the near-contempt in which his young ancestor held him, Raymond went on blandly: "Anyhow, Conrad took it upon himself to feel particularly guilty, because, he decided, if it hadn't been for the fact that our great-grandfather discovered the super-drive, we might never have reached the stars.
output:  They bribed the assistant for the plans and blackmailed or tortured someone to build the time transmitter for them.
options:  They bribed the assistant for the plans and blackmailed or tortured someone to build the time transmitter for them.  Professor Farkas' assistant sent them back in time using the time transmitter after they gave him a bribe.  They bribed the assistant for the plans and hired a gadget enthusiast to build the time transmitter for them.  Professor Farkas sent them back in time with the time transmitter.