An aluminum pipe column (E = 10,400 ksi) with length L = 10.0 ft has inside and

Question:

An aluminum pipe column (E = 10,400 ksi) with length L = 10.0 ft has inside and outside diameters d1 = 5.0 in. and d2 = 6.0 in., respectively (see figure). The column is supported only at the ends and may buckle in any direction.
Calculate the critical load Pcr for the following end conditions:
(1) pinned-pinned,
(2) fixed-free,
(3) fixed-pinned, and
(4) fixed-fixed.