Ubuntu :: Creating Script For Calculating Payments

Recently I was trying to make a quick script for calculating payment between workers. I got stuck however. Here is what I am in for...

#!/bin/bash
#Setting the calculator
calc=` bc << EOF
scale=4
a=$2*($3/100)
b=$4
a/b
EOF
`
I've saved the $1 for further script.
#Creating the script
while [ -n $1 ]
do
case $1 in
workerA) read -p "Enter the total sum: " total
total=$2;
read -p "Enter the percentage:" percent
percent=$3;
read -p "Enter number of workers:" workers
workers=$4 ;;
*) echo "Error usage!"
break
esac
done

My script ends here. It just does not work. Did I sat the vars in the wrong way?