Shell Script to find area of circle,rectangle,square and pentagon

echo "1.Area of circle"
echo "2.Area of Rectangle"
echo "3.Area of Square"
echo "4.Area of Pentagon"
echo "enter the choice of operation:-"
read c
case $c in
1)
echo -n "Enter radius of circle:- "
read r
echo -n "Area of circle is :- $carea"
carea= echo "3.14 * $r * $r" | bc
;;
2)
echo -n "Enter Length of Rectangle:- "
read l
echo -n "Enter Breath of Rectangle:- "
read b
rarea=`expr $l \* $b`
echo "Area of Rectagle is:- $rarea"
;;
3)
echo -n "Enter Length of Square:- "
read l
sarea=`expr $l \* $l`
echo "Area of Square is:- $sarea"
;;
4)
echo -n "Enter apothem length of Rectangle:- "
read a
echo -n "Enter side of the Pentagon:- "
read s
echo -n "Area of Pentagon:- "
parea= echo "2.5 * $s * $a" | bc
;;
*)
echo "wrong input"
;;
esac