A tubular aluminum column $($E $=10,400$ ksi$)$ with a length L $=10\mathrm{.}0$ ft has interior and exterior diameters $=5\mathrm{.}0$ in$.$ and $=6\mathrm{.}0$ in$.,$ respectively $($see the figure$).$ The column is supported only at the ends and can buckle in any direction.Calculate the critical load for the following end conditions:$1.$pinned$-$pinned$2.$fixed$-$free$3.$fixed$-$pinned$4.$fixed$-$fixed