FYI, I had someone who was competent at math look at this formula because I was suspicious of its validity since the Nemeth code seems to miss this situation so completely. It seems this is an issue because there is a misprint in the text and the (ln) should be accompanied by the number 2 to make this formula work correctly. This is also alluded to in the text that precedes the problem as well. We are unfortunately confined to follow the print and feel very bad for this student. This book seems to contain many such errors.