Maxwell's Rainbow Problem frequency/wavelength

[arl146]

Homework Statement

A certain helium-neon laser emits red light in a narrow band of wavelengths centered at 632.8nm and with a wavelength width if .01nm. What is corresponding frequency width for the emission?

Homework Equations

f=c/$\lambda$ ?

The Attempt at a Solution

I tried using the above with both numbers given. This is supposed to be an easy problem, but i think there's something I am missing here... Answer is 7.49GHz?

 

[arl146]

are you supposed to use both numbers given.. this has to be easier than I am thinking