Mass of a mass-spring system, if amplitude of the moving mass is given

Question

1. A mass m is attached to a spring is subjected to a harmonic force as shown in figure. The amplitude of the forced motion is observed to be 50 mm. The value of m (in kg) is

   

                                                                                        

           a) 0.1                             (b) 1.0                          (c) 0.3                             (d) 0.5