The extension of a circular bar tapering uniformly from diameter d₁ at one end to diameter d₂ at the other end and subjected to an axial pull of P is given by

A. δl = 4PE/ πl²

B. δl = 4πld²/PE

C. δl = 4Pl/πEd₁d₂

D. δl = 4PlE/ πd₁d₂

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