Determine the allowed range of the diameter of the copper core.

A copper–silver bimetallic wire, 1 cm in diameter, is prepared by co–extrusion with copper as the core and silver as the outer layer. The desired properties along the axis parallel to the length of the bimetallic wire are as follows:

(a) Thermal conductivity /410 W/(m–K);

(b) Electrical conductivity / 60 × 10⁶Ω^-1m^-1; and

(c) Weight < 750 g/m. Determine the allowed range of the diameter of the copper core.