coefficient of speed fluctuation of a flywheel

Question

If C_f is the coefficient of speed fluctuation of a flywheel then the ratio of w_max/w_min will be  

a)$\frac{1-2C_{f}}{1+2C_{f}}$

b)$\frac{1-2C_{f}}{2+C_{f}}$

c)$\frac{1-2C_{f}}{1-2C_{f}}$

d)$\frac{2+C_{f}}{2-C_{f}}$