Shell Programming and Scripting

Task 2:

When Im tring script called char that checks a single character on the
command line, c. If the character is a digit, digit is displayed. If the
character is an upper or lowercase alphabetic character, letter is
displayed. Otherwise, other is displayed. Have the script print an
error message if the argument c is more than one character in length.

How to pass the alphabet characters as a argument in case and in if block? How to pass multiple numbers in a single case?
Help!! to correct the code

Code:

#!/bin/ksh
 
c=$1
if [[ c -le 9 ]]
then
echo "Proceed "
elif [[ c -eq a-z ]]
then
echo "alphabet"
else
echo "More than one char in length"
fi
 
case $1 in
 
1-9) echo "The value is a number"
;;
a-z) echo "the value is a alphabet"
;;
*) echo "Other"
;;
esac