$4\mathrm{.}198$ The four forces shown are applied to a rigid plate supported by a solid steel post of radius $a.$ Knowing that $P=24$ kips and $a=1\mathrm{.}6$ in$.,$ determine the maximum stress in the post when $(a)$ the force at $D$ is removed, $(b)$ the forces at $C$ and $D$ are removed. ANSWER is a$)-20\mathrm{.}9$ ksi b$)-22\mathrm{.}8$ ksi