Question on Homework 9 Question 6

Hello! I've been stumped on this for at least two nights in a row, though I should've asked earlier.

I can't figure out how to actually do part C – however I try to do it (with the result from the dot product of A and the unit vector Q / \|Q\|) it just isn't correct.
I know I'm probably not gonna get a response in time to finish it but thought I should ask anyway just so I. know what I was doing wrong.

I guess that P and Q are both points, not vectors. Thus, the question is: what's the rate of change if you move from the point P=(-6,-5,0) heading towards the point Q = (-4,-7,-1)?

In that case, your displacement vector \vec{d} would be Q-P and \vec{u} = \vec{d}/\|\vec{d}\|.

I think you'll get 11/75 with that approach.

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Note: I would typically phrase the question in terms of P and \vec{d} directly on a quiz or exam.