#!/usr/bin/python 
# Both Rc and Sc have to be degree one polynomials

def pd(Rc,Sc,Ts):
    K = (Sc[0]+Sc[1])/(1+Rc[1])
    N = (Sc[1]-Sc[0]*Rc[1])/Rc[1]/(Sc[0]+Sc[1])
    taudbyN = -Ts*Rc[1]/(1+Rc[1])
    taud = taudbyN * N
    return K, taud, N