Two iron-constantan thermocouples with 1 and 2 mm diameters of the junctions are dipped into boiling water (100oC) from ambient temperature (20oC). The heat transfer coefficient of thermocouples equals to 3000 W/(m2C). Assume that junctions of thermocouples are spherical and contain 30% of costantan and 70% of iron (mass fractions). a. Calculate time constants of both thermocouples.