Kb Ka Ka Consider the two mass-spring systems above that will both vibrate in their longitudinal modes. All masses are the same, 10kg. If the spring constant of the bottom system (Ka) is 120N/m, what does the spring constant of the top one (Kb) have to be so that the frequency of its higher frequency mode of vibration is equal to the lower frequency mode of the bottom one? O 120 N/m O 40 N/m O 360 N/m O 208 N/m O 60 N/m