Without doing your homework for you, here are a few pointers. First, 'tr' translates between one character set and another (it also deletes and squeezes char sets), it cannot be used to correct words with wrong cases. For example:
echo "ronald REAGAN | tr [a-z] [A-Z]
What exactly should the correct case for 'Trust and Verify' be?
I would probably use sed, but there may be other utils.