A $2-$m$-$high, $5-$m$-$wide rectangular advertisement panel is attached to a $6-$m$-$wide, $25$ cm$-$high rectangular concrete block $($density $=2400$ kg$/$m$3)$ by two $8-$cm$-$diameter, $8-$ m$-$high $($exposed part$)$ poles, as shown in the figure. If the sign is to withstand $150$ km$/$h winds from any direction, determine $($a$)$ the maximum drag force on the panel, $($b$)$ the drag force acting on the poles, and $($c$)$ the minimum length L of the concrete block for the panel to resist the winds. Take the density of air to be $1\mathrm{.}25$ kg$/$m$3.$ Take CD to be $0\mathrm{.}3$ for a circular rod and $2\mathrm{.}05$ for a flat rectangular plate perpendicular to the flow.