I need help in doing D and E since I am completely stuck and do not know how to proceed. For D though, I suspected at first that it would involve a derivative but then I read the "The formula should not involve A or x ." part which shut down that idea. As for E, it depends on D so I can't understand it at all!

If you have a specific question to ask me to get to know my perspective on the problem, just ask.

Any help would be greatly appreciated!

Thanks in advance!