These are in a textbook for practice puposes but there are no answers
to it. So thats where your help is needed:

A picture shop is producing teo sizes of picture frames. The large
frame sell for $25 each and the small frame for $19 each.

The cost per month is C=$5,500 +8Qs +12QL, where QS denotes the number
of small frames and QL the number of large frames.

1. Does the picture company make a profit on a small or large frame?
2.The company can expand production and sales of one types of frames,
but not both, Which should it expand. Explain.

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Clarification of Question by econ_student-ga on 14 Oct 2005 10:27 PDT

A picture shop is producing two sizes of picture frames....

The marginal profit on a small frame is: 19 - 8 = $11

On a large frame it is : 25 - 12 = $13

The break evens are:  
  Small:  5,500 = QS * 11   QS = 5,500 / 11 = 500 units

  Large:  5,500 = QL * 13   QL = 5,500 / 13 = 423.08 units 

Both sizes are potentially profitable, provided one exceeds the breakeven

The large frames are more profitable, so (given the current
information) one should increase production of large frames.