I am trying to figure this out but the book is not very specific with its terms so I am not sure what is actually meant by the author.
"Boyle's Law states that when a sample of gas is compressed at constant temperature, the pressure P and volume V satisfy the equation PV=C, where C is constant. Suppose that at a certain instant the volume is 600 $cm^3$ the pressure is 150 kPa and the pressure is increasing at a rate of 20 kPa/min. At what rate is the volume decreasing at this instant?"
I am trying to find the rate of change of V for PV=C when the volume is 600 where P is Pressure and the rate of change of P is 20. C is constant. I am not sure what is meant by constant. Something that is constant will have a derivative of 0 but that does not give me a correct answer. Am I missing anything?