Problem: what is the units digit of 33 ^ 2 * 17 ^ 3 * 39 ^ 2 ?
Rationale: "the units digit of 33 ^ 2 is the units digit of 3 * 3 = 9 which is 9 . the units digit of 17 ^ 3 is the units digit of 7 * 7 * 7 = 343 which is 3 . the units digit of 39 ^ 2 is the units digit of 9 * 9 = 81 which is 1 . the units digit of 9 * 3 * 1 = 27 is 7 . the answer is d ."
annotated_formula: divide(add(multiply(factorial(33), factorial(2)), multiply(factorial(33), factorial(3))), 33)