<p>A heat engine operates between a cold reservoir at temperature <span class="equation">\(T_2 \)</span>= 400 K and a hot reservoir at temperature <span class="equation">\(T_1\)</span>​​​​​​​. It takes 300 J of heat from the hot reservoir and delivers 240 J of heat to the cold reservoir in a cycle. The minimum temperature of the hot reservoir has to be ______________ K.</p>