A sphere, a cube and a thin circular plate are heated to the same temperature. If they are made of same material and have equal masses then which one of the three objects cools faster

According to Stefan's law, the rate of cooling is given by−dTdt=eσAmcT4−T04or    −dTdt∝ASince the surface area of the plate is maximum for the given mass and hence, the circular plate cools the fastest.