Calculating Ambient Electric Fields in Thunderclouds for Aircraft Safety

[Binkey24]

Sorry if i have posted under the wrong catagorie physics is new to me so I am still getting my head around it.

Here is the question that is giving me a bit of bother;
An airplane is flying through a thunder cloud at an altitude of 2km. If the cloud has a charge concentration of 40C at an altitude of 3km above the ground and -40C at 1km altitude. What is the ambient electric field exsperienced by the air craft?
Additional information k = 9 x 10^9 N-m/C^2)

so far i have think the equations to be used are F=kQ,Q2 / r^2

this is what i get when i fill the following information = (9*10^9)*(40)*(-40) / 1^2

this equaling -1.44^13
Am i going the right way about it or have i missed a few steps? any guidance would greatly be appreciated.

 

[rl.bhat]

Convert kilometer to meter.

 

[Binkey24]

After changing the km into meters

(9*10^9) * (40) * (-40) / 1000^2

this gave me answer of = - 14400000
this answer seems a little big. or is it meant to be this large?

 

[glueball8]

Hmm 40C is wayyy too big. But anyways, your not answering the question. What is the electric field experienced by the plane question mark. (Sorry keyboard problems)

 

[Prob]

Not sure if I can help at all, I'm stuck in the same place. I think we are studdying the same thing.

 

[Prob]

Just found this, hope it helps:

See attachment, it didn't want to past in here.

Edit: Note the diference in k from your original question.