Father and son

Dear Dad,
$chool i$ really great! I've been 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

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 that you
can never study eNOugh.
Love,
Dad