Ok so n=70, I hope it’s right:)
Friday, magnitude doesn’t depend on if it’s negative or not
So it’s -12
We can employ some logic to reduce the answers we need to test. We know that the slope perpendicular to line l has to have a negative reciprocal slope, so a slope of
. We see that in A and C, as x increases so does y. That means the slope of these equations are positive, which we don't want. Now for some algebra:

We se that D has the correct slope so that must be the answer.