How do you learn pie?

Idon’t quite understand this problem

Explain why electric current cannot exist if a current doesn't have a voltage source.

The magnitude of the poynting vector of a planar electromagnetic wave has an average value of 0.939 w/m^2 . the wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. how much total electromagnetic energy falls on the area during 1.0 minute?