Simple shell script

I need to write a little script that finds the sum and average of the arguments entered on the command line.

scriptname 34 76 139 57 327
The sum is $sum
The average is $avg

I'd also like to write a script that can tell how many Sundays there were in the year 2000.

scripting practice

Ok, I figured out the first one.

#!/bin/sh
# find sum of command line arguments
a=0
for x in $*
do
a=`expr $a + $x`
done
echo Total is $a
# find and print average
b=`echo "scale=2; $a / $#" | bc`
echo Average is $b