<p>You are correct. Or you could think of it in another way: the rate “leaving” is always 800, the rate “entering”, r(t), is initially >800, which means that the line is currently increasing. Therefore, you simply need to find the time when the rate “leaving” is equal to the rate “entering” - which is 800. (And I use quotes because I don’t remember the actual context of the question’s story)</p>
<p>I thought the structure for most of the AB FRQs was similar to past exams. The piece wise definitely threw me off at first, but I think I at least scored half of the points on it. I could see myself getting a 5 on this, but I’d be fine with a 4.</p>