A cylindrical resistor of length L = 2 cm is constructed from an inner cylindrical core of radius R1 = 3.0 mm, made from material of resistivity r1 = 1.5 ohm-cm and an outer shell, which has an inner radius equal to R1 and an outer radius R2 = 4 mm, made from material of resistivity r2 = 3.0 ohm-cm. What is the total resistance of this device?