A micro oscillator is shown below. The "Proof Mass" is 0.02 gram. It is supported by two beams. The beam width (perpendicular to the paper) is 40 m; the other dimensions are shown in the figure. E=170GPa. 20m 800m Proof mass 800m 20m (a) [8 pts] Calculate the total stiffness by the two beams corresponding to motion in the vertical direction. (b) [7 pts] Calculate the natural frequency of the "Proof Mass" vibrating along the vertical direction.