A circular rod is tapered from one end to other end; the diameter at one end is \(2 \mathrm{~cm}\) and the diameter at the other end is \(1 \mathrm{~cm}\). Its length is \(20 \mathrm{~cm}\) long. On applying an axial load of \(6 \mathrm{kN}\), it was found to extend by \(0.068 \mathrm{~mm}\). Find the modulus of elasticity of the material of the rod.