BB Math question (p. 311 #15)

<p>I know the book has an explanation but it's unclear... </p>

<p>The answer in the book is (A) None, but I think it could be (C), III only...</p>

<p>Can't <T be directly below <S and directly right of <R? This would mean the slope of RT is zero and the slope of ST is undefined... Does undefined work in a sum (count as zero)? The sum would be und.+0+1... does that equal 1?</p>

<p>Thanks to anyone who takes the time to answer this.</p>

<p>Anyone have any info?</p>

<p>You can't add unef. + 1, so the answer is none of the above.</p>

<p>Excellent. Thank you.</p>