A built$-$up section is made by rigidly joining two $100-$mm x $100-$mm x $21,9-$

kg per metre steel equal angles to form a T$-$section having a flange width

of $200$ mm and a web of $100$ mm$.$ This section is used for an axially loaded

column such that when buckling about its stronger axis, both ends may be

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assumed pinned and when buckling about its weaker axis, the one end is to

be assumed pinned while the other is to be treated as built$-$in$.$ For a column

length of $6$ m$,$ calculate the least buckling load using both the Euler and the

Rankine formulae. Take E as $200$ GPa and the proportional limit stress as $200$

MPa. The Rankine constant for pinned ends is Which of the above two

formulae is more appropriate?