
$300-3 \theta=2 \theta-100+\theta$
$400=6 \theta$
$\theta=\frac{200}{3}^{\circ} \mathrm{C}$

$(i)$ a body with large reflectivity is a poor emitter
$(ii)$ a brass tumbler feels much colder than a wooden tray on a chilly day
$(iii)$ the earth without its atmosphere would be inhospitably cold
$(iv)$ heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water