Problem $2$: The steel frame supports a rotating machine that exerts a horizontal force at the girder level $F(t)=200sin(2\mathrm{.}3t)(lb).$ The frequency of force is equal to $2\mathrm{.}3ra\frac{d}{sec}.$ Assume $5\%$ of critical damping and determine: $($a$)$ The maximum displacement of a total vibration between $0$ to $10sec,$ and $($b$)$ The maximum dynamic stress in the columns. Assume the girder is rigid. please help me solve this problem both a and b