Situation 17.2 a Pair of Narrow Slits,separated by 1.8 Mm,is Illuminated by Illuminated

Situation 17.2
A pair of narrow slits,separated by 1.8 mm,is illuminated by a monochromatic light source.Light waves arrive at the two slits in phase.A fringe pattern is observed on a screen 4.8 m from the slits.
-In Situation 17.2,there are 5.0 bright fringes/cm on the screen.The wavelength of the monochromatic light is closest to:

A) 550 nm
B) 600 nm
C) 650 nm
D) 700 nm
E) 750 nm