A brass plug is to be placed in a ring made of iron. At 10°C, the diameter of the plug is 8.731 cm and that of the inside of the ring is 8.719 cm. a) They must both be brought to what common temperature in order to fit? b) What if the plug were iron and the ring brass? formula for thermal expansion: Δl = [itex]\alpha[/itex] * l0 * ΔT do i just equal Δl for brass and iron?