Docker Build - 404

Hi

I am new to docker as such and require help on the following issue.
I am using docker toolbox and trying to build an image , following is the command I use.
docker build --build-arg HTTP_PROXY=xxxxxxx–build-arg http_proxy=xxxxx.xx.xxxx.xx/xxxx --no-cache -t docker-whale .

The build fails at the step two of my dockerfile

following is my dockerfile

FROM docker/whalesay:latest
RUN apt-get -y update && apt-get install -y fortunes
CMD /usr/games/fortune -a | cowsay

Looks like the urls that the step 2 is trying to reach no more exists.
Below is the error I get. I have looked around in the forum and seems that this http://archive.ubuntu.com trusty/main Sources does not exist anymore and another url has to be used . My question this is url picked by the docker command , how do I change these url’s

Thanks
Amol

---------------------------------------------ERROR----------------------------------------------------------------

Err http://archive.ubuntu.com trusty/main Sources
404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
The command ‘/bin/sh -c apt-get -y update && apt-get install -y fortunes’ returned a non-zero code: 100