what is the units digit of 23 ^ 2 * 17 ^ 2 * 39 ^ 2 ?
"the units digit of 23 ^ 2 is the units digit of 3 * 3 = 9 which is 9 . the units digit of 17 ^ 2 is the units digit of 7 * 7 = 49 which is 9 . the units digit of 39 ^ 2 is the units digit of 9 * 9 = 81 which is 1 . the units digit of 9 * 9 * 1 = 81 is 1 . the answer is a ."
divide(add(multiply(factorial(23), factorial(2)), multiply(factorial(23), factorial(2))), 23)