what is the difference between the largest number and the least number written with the digits 9 , 3 , 5 , 7 ?
"explanation : 3579 9753 - - - - - - - - - - - - 6174 answer : e"
subtract(add(add(add(multiply(multiply(9, const_100), const_10), multiply(7, const_100)), multiply(3, const_10)), 5), add(add(add(const_1000, multiply(3, const_100)), multiply(7, const_10)), 9))