Boyle's Law states that when a sample of gas is compressed at a constant temperature, the pressure $P$ and the volume $V$ satisfy the equation $PV=C$, where $C$ is a 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?

$cm^3/min$