THERMAL PROPERTIES OF MATTER

The electrical resistance in ohms of a certain thermometer varies with temperature according to the approximate law :

R = Ro [1 + α (T – To )]

The resistance is 101.6 Ω at the triple-point of water 273.16 K, and 165.5 Ω at the normal melting point of lead (600.5 K). What is the temperature when the resistance is 123.4 Ω ?