Resistance R of a given conductor, at a constant temperature, is directly proportional to its length and inversely proportional to its area of cross-section A.
i.e., R∝Al or R=ρAl
where ρ is called the specific resistance of the material.
Given, ρ=25×10−6Ωm,l=1m,A=0.5m2 R=0.525×10−6×1 =50×10−6 =5×10−5Ω