Higher Partial Derivatives & Chain Rule (urgent) I'll have a test this evening, and I don't want to fail on a question like this, so please help me out! I will greatly appreciate for any help provided. The question: http://www.geocities.com/asdfasdf23135/advcal11.JPG My attempt: http://www.geocities.com/asdfasdf23135/advcal10.JPG From the solutions manual: http://www.geocities.com/asdfasdf23135/advcal12.JPG My first-order derivative is correct, but my second-order partial derivative Fjj is wrong. But I don't understand WHY I am wrong. Can someone please show me HOW to calculuate Fjj? I even tried to draw tree diagrams to clarfiy the dependence of variables, but I still got messed up, this is very very frustrating. I spent an hour looking through my work (I'm not kidding), but I can't locate my mistake, nor do I understand the way the solutions manual calculate Fjj. Thanks again!