A cylindrical resistor of length ℓ=2 cm and diameter d=0.5 cm has a voltage of 1 V applied between its ends. This voltage results in a current of 0.2 mA.
(i) Find the conductivity of the material out of which the resistor is made.
(ii) Next, the resistor is reshaped so that one half of its length remains the same while the other half has its diameter reduced to 0.25 cm. Find the total resistance of the bar.