calculation

Hi, I am in ksh88
I am trying to get the result of the calculation using 3 variables:
TOTAL
CAPACITY
and get the following error:
$DB_CAPACITY=(( $DB_SIZE * 100 / $TOTAL ))
ksh: syntax error: `((' unexpected
I cannot figure out what am I doing wrong... Thanks for any help -A

> DB_SIZE=5000
> TOTAL=200
> DB_CAPACITY=$((DB_SIZE * 100 / TOTAL))
> echo $DB_CAPACITY
2500
</> DB_CAPACITY=`expr $DB_SIZE \* 100 / $TOTAL`