The figure below shows cost (blue) and revenue (black)
functions over the domain 0<q<15 (in thousands of units).

*(Click on the graph to get a larger version.)*

For what production levels is the profit function
positive?

*(Give your answer as an interval or a list of intervals,
e.g.,* **(-infinity,8]** *or*
**(1,5),(7,10)** *.)*

For what production levels is the profit function
negative?

*(Give your answer as an interval or a list of intervals,
e.g.,* **(-infinity,8]** *or*
**(1,5),(7,10)** *.)*

Estimate the production at which profit is maximized.

You can earn partial credit on this problem.