Equation (8.14) is one formulation of the Friis free-space

Equation (8.14) is one formulation of the Friis free-space equation. Show that this equation can also be formulated in the following equivalent forms: where Pt is the transmitted power, At is the effective area of the transmitting antenna, ? is the carrier wavelength, d is the distance of the receiver from the transmitter, G is the power gain of the receiving antenna, A. is the effective area of the receiving antenna, and P, is the received power. Discuss the situations that favor the use of one of these equations over the other.