The most powerful 5G antennas work with a power of 120W. Assume that the human head is a sphere with a radius of 10 cm and that the human body is predominantly made of water. For simplicity, you can also assume that the antenna transmits radio waves in all directions evenly. Estimate the upper limit (worst case scenario) of how much energy is captured by the human head if we stand just below the antenna (5 m from the antenna). Indicate which laws and concepts you used in the calculation.