Let ∈r₁ = 2.5 for 0 < y < 1 mm, ∈_r2 = 4 for 1 < y < 3 mm, and ∈r₃ for 3 < y < 5 mm (region 3). Conducting surfaces are present at y = 0 and y = 5 mm. Calculate the capacitance per square meter of surface area if

(a) Region 3 is air;

(b) ∈_r3 = ∈_r1;

(c) ∈_r3 = ∈_r2;

(d) Region 3 is silver.