Posted by **piper** on Wednesday, April 7, 2010 at 9:54pm.

The average cost per item, C, in dollars, of manufacturing a quantity q of cell phones is given by

C= (a/q) + b

where a and b are positive constants

a.Find the rate of change of C as q increases. What are its units?

b. Currently, 5000 phones are being made and production is increasing at a rate of 100 cell phones per week. How fast is the average cost changing if a = 200000? Is the average cost increasing or decreasing?