A reciprocating engine, running at 80 rad/s, is supported on spring. The static deflection of the spring is 1 mm. Take $g=10m/s^{2}$. When the engine runs, what will be the frequency of vibrations of the system?
(a)80 rad/s
(b) 90rad/s
(c)100rad/s 
(d)160rad/s 