For the given frame, assuming the horizontal girder may be infinitely rigid and the mass of the columns are negligible. Find the following: 1. Compute the natural frequency of the steel frame. 2. Compute the max. horizontal displacement at the given level for the following load functions, assuming no damping. (i) A force of 4k applied suddenly at t=0 and removed suddenly at t=0.3s. (ii) a force of 4 kip applied suddenly at t=0 and decreasing linearly to zero at t=0.5s. 3. Also determine the max. shear, moment and bending stress in each column for the rectangular impulse. Compare the max. static bending stress to dynamic bending stress.