how to check for division by zero

i have a script that is doing the following:

awk 'BEGIN {FS=","} ; {printf("%.10f",($5 - $2)/(3 * $3))}' data > test

now some records in $3 contain zeroes. i don't want to remove those records. is it possible to check for division by zero and then write a "N/A" for that record in the o/p file (in this case test)?
thanks

awk 'BEGIN { FS = "," }
$3 ~ /[1-9]/  { printf "%.10f", ($5 - $2)/(3 * $3)  }
$3 !~ /[1-9]/ { print "N/A" }
'

ok that worked.. thanks..