1. The problem statement, all variables and given/known data The average cost per item, C, in dollars, of manufacturing a quantity q of cell phones is given by the following equation, where a and b are positive constants. C = a/q + b (a) Find the rate of change of C as q increases. Include units. I already found this, it's: -a/q^2 ***(b) If production increases at a rate of 130 cell phones per week, how fast is the average cost changing? Include units. B is the one I need help with. 3. The attempt at a solution So far for part "b", I've figured out that dq/dt is 130, so I differentiated C = a/q + b implicitly and got dC/dt = -a/q^2 (dq/dt) + b. I plugged in 130 for dq/dt and got dC/dt = -130a/q^2 + b I have no idea where to go from here. Any help would be greatly appreciated!