For constants a ,b, n, r, van der waals equation relates the pressure p to the volume v of a fixed quantity of a gas at constant temperature t:

(p + (n^2 * a)/v^2)(v−nb) = nrt

find the rate of change of volume with pressure dv/dp

Base on your question where a constant A,B,N, R Van der waals equation relates the pressure P to the volume C at fixed quantity of gas at constant value of Temperature T and the ask is to find the rate of change of volume with the pressure dV/dP and the rate of change is 
dP/dV=(P+n2a/V2)/(nb−V)+2n2a/V3

50% of students voted for candidate b.