the unit digit in the product ( 635 * 767 * 984 * 489 ) is :
"explanation : unit digit in the given product = unit digit in ( 5 * 7 * 4 * 9 ) = 0 answer : a"
subtract(multiply(multiply(multiply(635, 767), 984), 489), subtract(multiply(multiply(multiply(635, 767), 984), 489), add(const_4, const_4)))