What is the total number of independent elastic constants required to completely define a 3D orthotropic material?

A steel rod with a circular cross-section of diameter 1 cm and another steel rod with a square cross-section of side 1 cm have equal mass and length. If both rods are subjected to the same tension, the ratio of the elongation of the circular rod to that of the square rod is:

The length of a conical bar is l, the diameter of the base is d, and the weight per unit volume is w. It is fixed at its upper end and hangs freely. The elongation of the bar under the action of its own weight will be: