what is the units digit of 32 ! + 50 ! + 2 ! + 4 ! ?
"for all n greater than 4 , the units digit of n ! is 0 . the sum of the four units digits is 0 + 0 + 2 + 4 = 6 the units digit is 6 . the answer is d ."
add(add(const_4, const_3), const_2)