1. The problem statement, all variables and given/known data Solve 3 equations in three unknowns I, W, and L to find the critical value of L. ***Please See attachment 'differential.gif'**** also note, that I wrote all this using 'mathtype', if its of importance for any to know. 2. Relevant equations Please see attachment 'differential.gif' 3. The attempt at a solution ****Please see attachment 'Differential tryout.gif' and 'Differential Tryout2.gif'*** I squeezed my brain to what it can handle, but I can not understand how the textbook has got such a solution by its process which I do not understand------Please see attachment 'Differential textSolution.gif' ( since their is a max of three attachments, I am gona make a new thread named 'Differential Text sol' with the attachment.