$[1]$ A small hole with a diameter $d=0\mathrm{.}09cm$ was drilled into a diameter $D=1$ cm rod under the impact load in the direction perpendicular to the axis as shown in the figure. Compare the capacity of the shock energy absorption when the hole is not drilled and when the hole is drilled $($Unhole$/$Uhole$).$ However, Ki is the stress concentration coefficient, and the volume change due to the small hole is negligible, but the area reduction of the small hole is not negligible. $[25$ points$]$