If you could shine a very powerful flashlight beam toward the Moon, estimate the diameter of the beam when it reaches the Moon. Assume that the beam leaves the flashlight through a 4.0-cm aperture, that its white light has an average wavelength of 550nmnm, and that the beam spreads due to diffraction only. The distance from the Earth to the Moon is 38410^3km.

Express your answer to two significant figures and include the appropriate units.