Determine the rate at which sales are changing at a time when x = 50, p = 10, and the price is falling at the rate of $0.50 per week. (Thanks in advance!) 2. Differentiate your equation, sub in what you are given and find dx/dt.$\displaystyle 6p^{2}\frac{dp}{dt}+2x\frac{dx}{dt}=0\$