Figure P11.2 shows the cross sections of two aluminum alloy 2114-T6 bars...

Figure P11.2 shows the cross sections of two aluminum alloy 2114-T6 bars that are used as compression members, each with effective length of L_e. Find (a) the wall thickness the hollow square bar so that the bars have the same cross-sectional area; (b) the critical load of each bar. Given: L_e = 3 m and E = 72 GPa (from Table D.1).