The Magnetic Field of a Plane-Polarized Electromagnetic Wave Moving in the Z-Direction

Multiple Choice

The magnetic field of a plane-polarized electromagnetic wave moving in the z-direction is given by
$$B = 1.2 \times 10 ^ { - 6 } \sin \left[ 2 \pi \left( \frac { z } { 240 } - \frac { t \times 10 ^ { 7 } } { 8 } \right) \right]$$
in SI units.Find the average power per square meter carried by the EM wave.

A) 720 W
B) 172 W
C) 500 W
D) 2 * 10⁷ W
E) 86 W