A resistance thermometer reads R = 20.0Ω, 27.5Ω, and 50.0Ω at the ice point (0°C), the steam point (100°C) and the zinc point (420°C) respectively. Assuming that the resistance varies with temperature as Rθ = Rθ (I + αθ + βθ2), find the values of Rθ, α and β. Here θ represents the temperature on the Celsius scale.