1. The problem statement, all variables and given/known data http://img76.imageshack.us/img76/7307/staticsir4.jpg [Broken] 2. Relevant equations i dont know :( 3. The attempt at a solution I tried but the working is in a notepad, plus I wasnt getting anywhere anyway! I know its a long questions but this example is essential to my study, any help is largely appreciated! Thanks in advance!