Dear Dad,
$chool i$ really great. I am making lot$ of friend$ and $tudying very hard. With all my $tuff, I $imply can`t think of anything I need. $o if you would like, you can ju$t $end me a card, a$ I would love to hear from you.
Love,
Your $on

Dad's reply:

Dear Son,
I kNOw that astroNOmy, ecoNOmics, and oceaNOgraphy are eNOugh to keep even an hoNOr student busy. Do NOt forget that the pursuit of kNOwledge is a NOble task, and you can never study eNOugh.
Love,
Dad