. In an aluminum (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure.

In an aluminum (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure. The electrical resistivities of Al and Fe are 2.7 × 10^-8 Ωm and 1.0 × 10^-7 Ωm, respectively. The electrical resistance between the two faces P and Q of the composite bar is