4. In Figure 3, current is set up through a truncated right circular cone of resistivity ρ, left radius a, right radius b, and length L. Assume that the current density is uniform across any cross section taken perpendicular to the length. (a)What is the resistance of this cone? (11)_______ (represented with ρ, a, b, and L.) (b) This cone was made from copper material. Taking ρ = 1.69×10⁻⁸ Ω·m for copper at 293 K, left radius a= 0.20 mm, right radius b= 0.60 mm, and length L = 10.0 cm, calculate the resistance of the cone. (12)_______ (c) Taking the temperature coefficient of resistivity, α = 4.3 × 10⁻³ K⁻¹ for copper, re-estimate the resistance at 400 K. (13)_______. [Hint: ρ= ρ₀(1+α·ΔT), where ΔT is the change of temperature.]