6. The frame shown in the figure is clamped at the left end and supported on a hinged roller at the right end. An axial force P and a couple C act at the right end. The load factor for the axial force is 1.5 and that of the couple is 2.0. Determine the radius of the circular cross-section. Assume the following numerical values: L = 1 m, E = 80GPa, P = 15,000N, C = 1,OOONm, ay = 250 MPa.

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