A 1.50-m cylindrical rod of diameter 0.500 cm is connected to a power supply that maintains a constant potential difference of 15.0 V across its ends, while an ammeter measures the current through it. We observe that at room temperature (20.0°C) the ammeter reads 18.5 A, while at 92.0°C it reads 17.2 A. We can ignore any thermal expansion of the rod. Find a. the resistivity at 20.0°C and
b. the temperature coefficient of resistivity at 20.0°C for the material of the rod.