The natural frequency of a simple spring-mass system

Question

As shown in Figure, a mass of 100 kg is held between two springs. The natural frequency of vibration of the system in cycle/s, is

 

(a)   $\frac{1}{2\pi }$                                                              (b) $\frac{5}{\pi }$

(c) $\frac{10}{\pi }$                                                                  (d)$\frac{20}{\pi }$