An electric heater is rated at $500 \mathrm{W}$.
a. How much energy is delivered to the heater in half an hour?
b. The heater is being used to heat a room containing $50 \mathrm{kg}$ of air. If the specific heat of air is $1.10 \mathrm{kJ} / \mathrm{kg} \cdot^{\circ} \mathrm{C},$ and 50 percent of the thermal energy heats the air in the room, what is the change in air temperature in half an hour?
c. At $\$ 0.08$ per kWh, how much does it cost to run the heater $6.0 \mathrm{h}$ per day for 30 days?