How do I write a shell script file to read 5 student names (First and Last name) and their grades using a While Loop? Find the Average, Maximum, and Minimum of grades using the same While Loop. Prompt the user using tput to enter the information (first name, last name, grade). Save the data in a file called students.txt. Sort the file by last name and display it on the screen. Someone gave me this to go buy but im way basic and am not sure if there is anything missing from this. I also need to be able to use Tput.
If anyone can help me get this done or tell me whats missing id appreciate it.

1. suppose file is of form "Name Surname Grade"

#!/bin/zsh

sum=0
min=10000
max=0
n=5
i=0
file="students.txt"

cat $file | while read line; do
set line
grade=$3
sum='expr $sum + $grade'
if [ $grade -gt $max ]; then
max=$grade
fi
if [ $grade -lt $min ]; then
min=$grade
fi
i='expr $i + 1'
if [ $i -ge $n ]; then
break
fi
done

average='expr $sum / $i'
echo "Max: $max Min: $min Avg: $average"

We have a pretty strict policy here about not allowing homework questions. I'm locking this thread.