How fast does the blue pulse travel?

[burgerkin]

Homework Statement

A beam of red light entering a block of glass (n = 1.52) 10.00 miles thick will emerge 1.75 miles ahead of a blue pulse that entered at the same moment.
(a) How long will it take the red light to traverse the glass?
µs
(b) How fast does the blue pulse travel?
m/s
(c) How much time will elapse between the emergence of the red and then the blue?

Homework Equations

v=f\lambda
\lambda1 /\lambda2 =v1 /v2 =n2 / n1

The Attempt at a Solution

Here is what I tried

\lambda=700 nm for red light

700 / x = 1.52 /1
x=461 nm (x is the wavelength when red light passes thru the glass)

then

460nm x 4 x 10^14 =1.84 x 10^8 m/sI am not sure if it is correct, and what really is the distance the red light traveled? 10-1.75 miles??thanks n advance

 

[burgerkin]

Could anybody help me out? thanks! waiting online.