What is the acceleration of an electron in an electron gun?

[alijan kk]

Homework Statement

Q; In an electron gun of television set, an electron with initial speed of 10^3m/s enters a region where it is electrically accelerated. It emerges out of this region after 1micro sec with speed of 4×10^5 m/s.

(a) Find the acceleration.

Homework Equations

vf= vi+at

The Attempt at a Solution

vf = vi+at
400000= 1000+a*0.000001
400000-1000= a*0.000001
399000=a*0.000001
399000/0.000001= a
3.99×10^11= a
a= 3.99×10^11


The ans in book is 3.99×10^9

Which ans is right ?
Any help would be appreciated :-) :-D ,
Thank you

 

[Hamal_Arietis]

$4.10^5=10^3+a.10^{-6}$
Your ans is right

 

[alijan kk]

$4.10^5=10^3+a.10^{-6}$
Your ans is right

My ans is right !
That means book has a mistake,
Thanks