I'm currently studying an engineering degree with the Open University, but have come across this question in one of my revision quizzes which I have no idea how to work out. The way they told me I should have worked it out also makes no sense to me, so I'm hoping someone could talk me through it.
I've posted the same post on the Open University forums, but had no responses. I've taken a screenshot of it and included it here, as i think the equations are a bit easier to read in the screenshot.
Thanks in advance!