So... the answer is "impossible to know"? There's no data on how many seats there are, their distance, or whatever. There could theoretically be literally just the seat you're sitting on in the entire system. Then the answer is zero.
Let's neglect the horizontal distance the chair(s) travel at the bottom and at the top of the lift. Then the answer is "all of them," which holds true in your one-chair scenario.
The question reminds me of "how many groves are there on a vinyl record?"
Since I don't drink coffee, you are unlikely to ask me that question. But if you did, I might assume you are either joking or an idiot ;).
Clearly, it's a trick question (with unnecessary details to distract you from a possible solution) and the one asking probably thinks they are very clever. So now, whether you accept an equation or insist that it's impossible to solve when it's not really comes down to how you want to play that game.
