I've been given an optimization and related rates writing assignment by my professor but I missed the past class where we covered how to do the problems so I'm unsure how to go about it. I was just wondering if you guys could point me in the right direction for a few of these problems?

Here is the assignment: http://pastebin.com/gM2YVJ9P

And here is what I have so far: https://www.dropbox.com/s/ow7na1vxlc...20inflated.pdf

I've completed problem 1, am clueless for problem 2, and have done most of problem 3 and 4.

Here are my questions:

- Does my work for problem 1 look correct?
- How do I start/do number 2? I can't find any good examples to pull from in my book or online..
- What exactly does he mean by "find the derivative of the cost" in problem 3? Does he simply want me to find the derivative of 5,100,000? That wouldnt make much sense or help on the last part of this problem..
- As for problem 4.. I'm pretty sure I did it wrong and I'm not sure how to finish the last part of the problem.