$2\mathrm{.}14.$ The one$-$story structure shown in Fig. $2\mathrm{.}21$ can be modeled in the first approximation as a single$-$degree$-$of$-$freedom system by regarding the columns as massless beams clamped at both ends and the roof as a rigid slab. Derive the equation for the horizontal translation of the slab and determine the natural frequency. The mass of the slab is denoted by $M$ and the flexural rigidity of the columns by $EI.$

FIGURE $2\mathrm{.}21$

One$-$story structure