UNIX Program to check the entered word starts with vowel, ends with a digit or it is just three-letter word

Write a program to check the entered word starts with vowel, ends with a digit or it is just three-letter word.
echo Enter a word
read word

case $word in
[aeiou]*) echo "it starts with vowel";;
*[0-9]) echo "ends with number";;
[a-z][a-z][a-z]) echo “it is a 3 letter word”;;
*) echo “you have entered an invalid word”;;
esac