A 20 Kg Mass Hangs on a Spring with a 1

A 2.0 kg mass hangs on a spring with a 1.1 newton/meter force constant and its motion is not damped. If the system is subjected to an external variable-frequency vibration described as newtons, at what frequency, , will the external vibration and the spring system be in resonance?

A) 0.55 s^-1
B) 0.74 s^-1
C) 1.82 s^-1
D) 1.35 s^-1