P_{2} = K (30^{\circ} C - 18^{\circ} C) = 12 K = \frac{12 \cdot 1 W}{7} = 1, 7 W

${P_2 = K({30}{^{\circ}C} - {18}{^{\circ}C}) = 12K = \frac{12 \cdot {1}\,\mathrm{W}}{7} = {1,7}\,\mathrm{W}}$